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Fish investigations in the Barents Sea Winter 2022

Author(s): Johanna Fall , Thomas de Lange Wenneck , Bjarte Bogstad , Edvin Fuglebakk , Jane Aanestad Godiksen , Åge Høines , Knut Korsbrekke , Malin Lie Skage , Arved Staby , Caroline Aas Tranang , Kristin Windsland (IMR), Alexey A. Russkikh (PINRO) and Sergey Kharlin (PINRO)

Preface

Annual catch quotas and other regulations of the Barents Sea fisheries are set through negotiations between Norway and Russia. Assessment of the state of the stocks and quota advice are based on survey results and international landings statistics. The results from the demersal fish winter surveys in the Barents Sea are an important source of information for the annual stock assessment.

The development of the survey started in the early 1970s and focused on acoustic measurements of cod and haddock. Since 1981 it has been designed to produce both acoustic and swept area estimates of fish abundance. Some development has taken place since then, both in area coverage and in methodology. The development is described in detail by Jakobsen et al . (1997), Johannesen et al . (2009) and in Appendix 2, and the current survey design and methods for survey index calculation are presented in Appendix 1. At present the survey provides the main data input for several ongoing projects at the Institute of Marine Research, Bergen:

  • monitoring abundance of the Barents Sea demersal fish stocks

  • mapping fish distribution in relation to climate and prey abundance

  • monitoring food consumption and growth

  • estimating predation mortality caused by cod

This report presents the main results from the surveys in January-March 2022. The surveys were performed with the Norwegian research vessels “Helmer Hanssen” and “Johan Hjort”, and the Russian research vessel “Vilnyus”. Annual survey reports since 1981 are listed in Appendix 4, and names of scientific participants in 2022 are given in Appendix 3.

1 - Survey operation

Table 1.1 presents the vessels participating in the survey in 2022 and IMR trawl station series numbers, and Figure 1.1 shows survey tracks, trawl stations and ice cover.

  Period Series no.
Johan Hjort 27.01-18.03 70001-70216
Helmer Hanssen 18.01-16.02 70301-70457
Vilnyus 21.01-22.02 70501-70645
Table 1. 1. Vessel participation by period and trawl station series numbers by vessel for the winter survey in 2022.

 

Survey tracks and all trawl stations in the winter survey 2022. Data source for the ice cover: https://cryo.met.no/archive/ice-service/icecharts/quicklooks/2022/ (18.01.22, the first day of the survey).
Figure 1.1.Survey tracks and all trawl stations in the winter survey 2022. Data source for the ice cover: https://cryo.met.no/archive/ice-service/icecharts/quicklooks/2022/ (18.01.22, the first day of the survey).

 

Main area Trawl type
Number of hauls 
A

B1

B2

P

51

1

3

B

B1

B2

P

36

-

-

C

B1

B2

P

18

-

-

D

B1

B2

P

132

1

3

D'

B1

B2

P

61

-

1

E

B1

B2

P

34

1

5

S

B1

B2

P

72

-

3

Inside standard strata system

B1

B2

P

404

3

15

N

B1

B2

P

69

-

1

Outside strata system B1

B2

P

21

-

-

Total

B1+B2

P

497

16

Table 1.2. Number of trawl stations by main area in the Barents Sea winter 2022. B1= swept area bottom trawl (quality=1 and condition<3), B2 =other bottom trawl, P=pelagic trawl, N=trawl stations in new strata. Refer to Figure 1.1. or Appendix 1 for a map of the main areas.

The coverage of the most northern and most eastern strata differs from year to year. The areas of these strata are therefore calculated according to the coverage each year. Table 1.3 gives the area covered by the survey every year since 1981. In that table “Extrapolated area” reflects the size of areas where some kind of extrapolations/adjustments have been made to take account of incomplete coverage (see also section 3.1). Table 1.4 summarizes the degree of coverage and main reasons for incomplete coverage in the whole period.

  Main Area     Extra- polated area
Year A B C D D' E S N Total excluding N excluding
1981-92 23299 8372 5348 51116 - - -   88135  
1993 23929 8372 5348 51186 23152 8965 16690   137642  
1994 27180 9854 5165 53394 36543 11417 17557   161110  
1995 26797 9854 5165 53394 58605 13304 24783   191904  
1996 26182 9854 5165 53394 54047 5738 11809   166190  
19971 27785 9854 5165 23964 2670 0 18932   88371 56200
19981 27785 9854 5165 23964 5911 3829 23931   100440 51100
1999 27785 9854 5165 43230 8031 5742 18737   118545  
2000 27173 9854 5165 52314 29438 14207 25053   163204  
2001 26609 9854 5165 53394 29694 15777 24157   164652  
2002 26594 9854 5165 53394 21914 15757 24689   157369  
2003 26621 9897 5165 52072 23947 6259 23400   147361  
2004 27785 9854 5165 53394 42731 4739 20760   164428  
2005 27785 9854 5165 53394 39104 19931 24648   179883  
20062 27785 9854 5165 53394 35302 13872 24691   170064 18100
20071 27785 9854 5165 23911 8498 20822 27858   123894 56700
2008 27785 9854 5165 53394 23792 18873 26313   165176  
2009 27785 9854 5165 53394 31978 15739 27858   171774  
2010 27785 9854 5165 53394 17882 18562 27858   160501  
2011 27785 9854 5165 53394 33432 16835 27858   174324  
20122 27785 9854 5165 53394 9917 17289 27858   151263 16700
2013 27785 9854 5165 53394 58183 21118 27858   203358  
20143 27785 9854 5165 53394 54800 29897 27858 58048 208754  
2015 27785 9854 5165 53394 45449 26541 27858 47263 196047  
2016 27785 9854 5165 53526 29266 20342 27630 54387 173568  
20172 27785 9854 5165 45493 12223 18524 27858 38786 146903 37460
2018 27785 9854 5165 53394 45193 23095 27630 44186 192117  
2019 27785 9854 5165 53394 56452 26788 27630 34035 207121  
20202 27785 9854 5165 53394 47002 11475 26881 21614 181557 25148
20212 27785 9854 5165 52848 33050 26897 27630 48777 183230 10933
2022 27785 9854 5165 53395 44972 26897 26095 27630 216297  
Table 1.3. Area (NM2) covered in the bottom trawl surveys in the Barents Sea winter 1981-2022, 1994-2022 are StoX estimates.

1 Russian EEZ not covered

2 Russian EEZ not completely covered (Strata 7 and 13 in 2006, Area D’ in 2012, strata 7, 13, 15, 7 and 20 in 2017, strata 17, 19, and 20 in 2020, and strata 16, 19, and 20 in 2021).

3 Additional northern areas (N) covered from this year.

Year Coverage Comments
1981-1992 ABCD  
1993-1996 ABCDD’ES  
1997 Norwegian EEZ, S Not allowed access to Russian EEZ
1998 Norwegian EEZ, S, minor part of Russian EEZ Not allowed access to most of Russian EEZ
1999 ABCDD’ES Partly limited coverage due to westerly ice extension
2000 ABCDD’ES Russian participation starts
2001-2005 ABCDD’ES Russian vessel covered where Norwegians had no access
2006 ABCDD’ES No Russian vessel, not allowed access to Murman coast
2007 Norwegian EEZ, S No Russian vessel, not allowed access to Russian EEZ
2008 ABCDD’ES Russian vessel covered where Norwegians had no access
2009 ABCDD’ES Reduced Norwegian coverage of Russian EEZ due to catch handling
2010 ABCDD’ES Reduced Norwegian coverage of Russian EEZ due to bad weather
2011 ABCDD’ES Russian vessel covered where Norwegians had no access
2012 ABCDD’ES No Norwegian coverage of Russian EEZ due to vessel problems
2013 ABCDD’ES No Norwegian coverage of Russian EEZ due to vessel shortage
2014 ABCDD’ESN Strata 24-26 (N) covered for the first time
2015 ABCDD’ESN Slightly reduced/more open coverage due to bad weather
2016 ABCDD’ESN No access to Russian EEZ, Russian vessel covered most of Russian EEZ
2017 ABCDD’ESN No Russian vessel, not allowed access to southwestern Russian EEZ
2018 ABCDD’ESN Russian vessel covered where Norwegians had no access
2019 ABCDD’ESN Russian vessel covered where Norwegians had no access
2020 ABCDD’ESN Reduced coverage of D’, E, and N due to bad weather, reduced survey time (medical emergency), and ice-cover
2021 ABCDD’ESN Reduced coverage of D’ and E due to ice cover and time constraints, and of area N due to ice cover.
2022 ABCDD’ESN Reduced coverage of D’ and E due to ice cover and time constraints, and of area N due to ice cover.
Table 1.4. Barents Sea winter surveys 1981-2022. Main Areas covered, and comments on incomplete coverage.

2 - Length and age material

Individual lengths are collected from all target species, while otoliths for age determination are taken from cod, haddock, and capelin. For cod and haddock, the otolith readings are key for splitting the survey indices by age.

For both the bottom trawl and acoustic estimates, cod with all otolith types (coastal cod included) are included in the estimations. Coastal cod is usually well under 5% of the total.

Table 2.1 gives an account of the sampled length- and age material from bottom hauls and pelagic hauls from 1994 onwards.

  Cod Haddock Golden redfish Beaked redfish Greenland halibut Blue whiting Capelin Polar cod
Year L A L A L L L L L A L
1994 57290 3400 40608 1808 3157 12389 525      
1995 66264 3547 37775 1692 3785 9622 583      
1996 61559 3304 34497 1416 2510 10206 587      
1997 35381 2381 30054 1003 5429 10997 675      
1998 39044 2843 12512 859 1739 9664 649      
1999 22971 2321 12752 926 1266 6677 397      
2000 31543 2871 25881 1426 1161 8739 546   9172 1860 3702
2001 36789 2998 30921 1657 1173 7323 499   8079 2402 5955
2002 45399 3730 58464 2057 1143 6660 688   10643 2387 7283
2003 59573 2857 54838 1883 1102 4654 657   10390 1742 2510
2004 40851 3175 51705 1874 1438 5507 459   11633 1994 6080
2005 33582 3216 67921 2060 835 5166 832   12482 1892 6052
2006 19319 2683 23611 1899 728 3356 962   6851 2232 1362
2007 16556 2954 26610 2023 798 4544 973 4657 5475 1186 203
2008 26844 3809 50195 2490 897 8568 1020 1350 13772 886 3166
2009 22528 3486 40872 2433 455 9205 807 891 7636 776 617
2010 30209 4085 35881 2367 429 8564 984 626 12337 1189 551
2011 26913 3959 29180 2260 286 6885 607 105 11073 829 1492
2012 17139 3020 33524 1854 574 5721 354 2441 11047 1256 601
2013 14525 2451 19142 1671 479 6087 263 1091 15962 1591 3517
2014 22624 4501 35940 2586 563 9310 444 1846 32811 3647 6879
2015 25401 3795 18483 2038 395 8933 541 1991 15578 300 408
2016 16636 3368 25423 2067 614 8668 425 2396 11423 150 681
2017 12402 2851 15689 1955 576 8898 448 4799 5140 671 578
2018 42462 5178 43294 3307 1211 11500 548 1443 16219 788 876
2019 16217 5260 15967 3072 761 8981 413 886 13771 821 748
2020 19971 3770 11047 1641 1040 11853 711 866 16801 745 1569
2021 13714 4020 15253 1950 810 11292 1076 1722 16179 1377 5567
2022 20294 4160 25161 2288 1176 9826 945 1520 18371 2072 4115
Table 2.1. Number of fish measured for length (L) and age (A) in the Barents Sea winter survey 1994-2022.

Table 2.2. shows the number of age readings per age for cod from 1994 onwards, while table 2.3 shows the same for haddock. The number of age samples for fish age 10+ increased in the second half of the time series, reflecting changing age composition in the stocks.

Age/Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
1994 283 354 392 652 571 363 124 54 37 16 19 3 2 - - - - - - -
1995 409 360 461 528 714 532 268 47 16 13 8 6 - - - - - - - -
1996 304 564 359 400 462 584 384 108 23 8 6 5 3 1 - - - - - -
1997 257 322 321 224 264 310 310 108 27 5 2 - - - - - - - - -
1998 331 311 445 425 220 242 257 193 39 6 3 - 1 - 2 - - - - -
1999 250 323 365 450 334 185 159 110 38 5 1 1 1 - - - - - - -
2000 256 365 470 491 578 340 119 66 50 12 4 2 1 - - - - - - -
2001 437 259 440 544 513 484 201 44 19 13 3 - - - 1 - - - - -
2002 162 650 478 661 607 506 345 90 16 7 3 - - - 1 - - - - -
2003 246 108 545 391 434 456 304 175 48 7 3 - 2 2 - - - - - -
2004 311 493 260 599 368 407 387 254 87 17 6 1 1 - - - - - - -
2005 341 386 619 309 565 306 388 196 56 21 3 2 4 1 - - - - - -
2006 291 364 423 521 234 430 194 162 68 18 6 3 - - - - - - - -
2007 295 258 474 358 453 205 369 159 95 22 10 6 1 - - - - - - -
2008 169 366 676 866 471 532 246 300 72 17 2 1 1 - - - - - - -
2009 319 276 445 635 695 420 292 124 120 24 9 2 1 - - - - - - -
2010 429 369 292 489 571 745 371 247 93 64 25 2 2 3 - - 1 - - -
2011 373 526 484 319 436 621 677 226 76 34 14 7 4 2 1 - - - - -
2012 275 214 319 330 198 303 504 415 100 47 25 10 9 2 1 1 - - - -
2013 149 251 232 330 296 188 282 426 215 38 20 8 5 1 1 - - - - -
2014 414 301 571 387 415 341 186 368 308 89 18 12 4 1 2 1 - - - -
2015 479 413 369 589 396 457 290 173 267 176 51 11 3 2 1 - - - - -
2016 235 529 405 484 678 437 418 323 164 178 86 20 15 3 3 1 1 - - -
2017 296 248 449 299 323 494 274 191 110 44 37 33 9 7 1 1 - - - -
2018 508 762 592 901 438 491 673 338 186 91 45 51 23 4 4 3 1 - - -
2019 465 632 892 651 839 435 356 508 149 66 17 10 6 8 2 1 - - - -
2020 265 523 755 830 585 673 432 305 310 88 41 11 16 10 10 7 - - - -
2021 270 235 537 630 683 503 445 226 145 103 32 12 6 1 6 3 - - - 1
2022 709 340 293 450 550 530 460 378 128 53 28 17 7 - 7 1 1 3 1 -
Table 2.2. Number of age samples from cod by age in the Barents Sea winter survey 1994-2022. Year-age combinations with < five aged individuals are highlighted in yellow. Abundance indices are still presented for ages with < five age samples but note the uncertainty level (c. f. tables 5.4 and 5.8). Biological parameters by age are presented for ages with a minimum of three age readings (c. f. tables 5.10-5.13).
Age/Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
1994 212 192 250 432 219 40 4 5 8 5 13 1 - - - - - -
1995 289 177 131 241 543 156 15 1 2 1 - 5 1 - - - - -
1996 225 236 155 106 228 343 52 9 - 1 - 2 1 - - - - -
1997 169 62 147 86 44 113 163 19 4 - - - 2 1 - - - -
1998 151 178 68 147 74 38 73 112 12 1 1 - - - 2 1 - -
1999 251 112 238 81 98 44 19 23 24 1 - 1 - - - - - -
2000 327 321 138 344 64 72 16 3 20 9 2 1 1 - - - - -
2001 388 339 430 99 315 26 23 3 3 3 8 1 2 - - 1 - -
2002 445 354 382 450 84 123 19 7 1 2 5 3 2 - - - - -
2003 376 234 154 268 298 42 32 5 3 3 3 1 1 - - - - -
2004 303 464 254 232 277 251 50 22 7 4 3 1 2 3 - - - -
2005 487 263 437 247 189 284 125 4 4 1 - - - - - - - -
2006 458 516 141 356 166 108 104 45 4 2 - 2 - - 1 1 - -
2007 422 404 372 116 257 107 51 34 15 4 2 - - - 1 - - -
2008 317 525 584 470 168 237 46 23 8 1 2 1 - - - - - -
2009 298 318 562 488 473 114 78 13 2 5 - 1 - - - - - -
2010 448 190 272 519 462 294 41 19 8 7 2 2 - - - - - -
2011 337 394 123 205 494 440 159 15 3 - - 2 1 - - - - -
2012 355 112 338 58 116 408 291 73 4 6 1 3 - - - - - -
2013 176 377 134 328 56 75 286 204 35 3 - - - - - - - -
2014 449 116 455 98 202 57 96 202 90 11 4 - - 1 - - - -
2015 429 371 88 524 81 160 43 110 123 55 6 3 1 - - - - -
2016 430 282 430 99 452 88 126 87 175 129 39 6 - 2 2 1 - -
2017 449 385 250 294 43 236 54 62 21 68 48 26 3 - - - - -
2018 704 696 596 372 424 62 160 45 44 35 56 48 19 3 - - - -
2019 644 630 679 486 211 187 39 46 14 24 7 12 8 3 - 1 - 1
2020 219 359 498 622 339 141 80 22 16 10 8 13 15 10 1 - - -
2021 439 68 244 373 501 172 51 19 5 5 4 3 6 2 - 1 - -
2022 618 301 68 243 305 437 99 16 4 4 6 - - 2 - - - -
Table 2.3 . Number of age samples from haddock by age in the Barents Sea winter survey 1994-2022. Year-age combinations with < five aged individuals are highlighted in yellow. Abundance indices are still presented for ages with < five age samples but note the uncertainty level (c. f. tables 6.4 and 6.8). Biological parameters by age are presented for ages with a minimum of three age readings (c. f. tables 6.10-6.13).

3 - Survey index calculation

Details on the calculation of survey indices, including StoX settings for different species are found in Appendix 1.

In 2022, the swept area and acoustic 1 estimation in StoX was based on the following biotic and acoustic snapshot files (versioned trawl and acoustic data):  

Cod and haddock 
biotic_cruiseNumber_0155_2022_UFJN_VILN_Vilnyus_2022-06-03T22.02.08.787Z  
biotic_cruiseNumber_2022204_Johan+Hjort_2022-03-28T22.02.52.009Z 
biotic_cruiseNumber_2022840_Helmer+Hanssen_2022-03-28T22.01.21.854Z  
echosounder_cruiseNumber_0155_2022_UFJN_VILN_Vilnyus_2022-08-01T22.00.00.044Z 
echosounder_cruiseNumber_2022204_Johan+Hjort_2022-03-18T23.00.12.395Z 
echosounder_cruiseNumber_2022840_Helmer+Hanssen_2022-03-17T23.00.00.935Z 
Redfish (three species) 
biotic_cruiseNumber_2022204_Johan+Hjort_2022-03-23T23.02.14.225Z  
biotic_cruiseNumber_2022840_Helmer+Hanssen_2022-03-23T23.01.02.197Z 
biotic_cruiseNumber_0155_2022_UFJN_VILN_Vilnyus_2022-06-07T22.02.26.378Z 
Greenland halibut 
biotic_cruiseNumber_0155_2022_UFJN_VILN_Vilnyus_2022-06-07T22.02.26.378Z  
biotic_cruiseNumber_2022204_Johan+Hjort_2022-03-23T23.02.14.225Z  
biotic_cruiseNumber_2022840_Helmer+Hanssen_2022-03-23T.01.02.197Z  
Blue whiting 
biotic_cruiseNumber_0155_2022_UFJN_VILN_Vilnyus_2022-06-07T22.02.26.378Z.xml 
biotic_cruiseNumber_2022204_Johan+Hjort_2022-08-15T22.01.45.892Z.xml  
biotic_cruiseNumber_2022840_Helmer+Hanssen_2022-08-18T22.02.26.845Z.xml  
Table 3.1 : Snapshot files used in the 2022 swept area and acoustic estimation, by species.

1 Acoustic estimation is done for cod and haddock only. The biotic files are used in the acoustic StoX projects to split the acoustic backscatter by age.

3.1 - Raising of indices

In 1997, 1998 and 2007 only the Norwegian exclusive economic zone (EEZ) and parts of the Svalbard area (S) was covered. The swept-area indices for cod, haddock, golden redfish, beaked redfish and Greenland halibut have therefore been raised to also represent the Russian exclusive economic zone (EEZ) (Mehl et al . 2016).

In 2006, there was not complete coverage in the southeast due to restrictions. The observations in the partially covered strata 7 were extrapolated to the full strata, and the observations in the partially covered strata 13 were extrapolated to the same area as covered in 2005.

In 2012 the coverage was incomplete in the eastern areas, and the cod and haddock swept area estimates within the covered area were raised by the “index ratio by age” observed for the same area in 2008-2011 (ICES 2012). The scaling factor (“index ratio”) for estimating adjusted total from <Total – area D’> was the average ratio by age for Total/(Total – area D’) in the years 2008-2011 (Aglen et al. 2012).

In 2017, the Norwegian vessel was not allowed to operate south of 70º 10’ N and west of 41º 00 º E, and no Russian vessel participated in the survey. Only a small part of strata 7 was covered, and strata 13, 15, 17 and 20 were not covered. The cod, haddock, Greenland halibut and beaked redfish swept area estimates and cod and haddock acoustic estimates within the covered area were raised following the same procedure as for 2012. The scaling factor for estimating adjusted total from <Total –strata 7 > was the average ratio by age for Total/(Total – (strata 7+13+15+17+20)) swept area indices in the years 2014-2016.

In 2020, coverage was incomplete in strata 17, 19, and 20, and the cod and haddock acoustic and swept area estimates were raised by the “index ratio by age” observed for these strata in 2018-2019. The scaling factor for estimating adjusted total from <Total – strata 17, 19 and 20> was the average ratio by age for Total/(Total – (strata 17+19+20)) in the years 2018-2019.

In 2021, coverage was incomplete in strata 16, 19, and 20. Indices in the partly covered stratum 19 were extrapolated to the entire strata. No trawling was done in stratum 20. As cod and haddock abundances generally are low there, the stratum was partly ice covered and did not have coverage in the last two years, this stratum was excluded from estimation. Only one trawl station was taken in stratum 16. Here the cod and haddock acoustic and swept area estimates were raised by the “index ratio by age” observed for these strata in 2019-2020. The scaling factor for estimating adjusted total from <Total – strata 16> was the average ratio by age for Total/(Total – strata 16) in the years 2019-2020.

4 - Total echo abundance of cod and haddock

Table 4.1 presents the time series of total echo abundance (mean sA multiplied by strata area and summed over all strata) of cod and haddock in the investigated areas.

  StoX
Year Cod Haddock Sum
1994 5282 3898 9180
1995 3671 2948 6619
1996 2789 1248 4037
19971 1355 832 2187
19981 2254 543 2797
1999 1517 771 2288
2000 2833 1534 4367
2001 2158 1488 3646
2002 1976 2247 4223
2003 3717 3570 7287
2004 1174 2087 3261
2005 1370 2519 3889
2006 1116 2541 3657
20071 675 2311 2986
2008 3510 6195 9705
2009 2452 5300 7752
2010 3526 5939 9465
2011 2967 3715 6682
2012 3478 4182 7660
2013 5026 3604 9656
2014 4847 2915 7762
2015 5245 2161 7406
2016 2879 1587 4466
20171 2139 2588 4732
2018 3537 2851 6388
2019 3282 3039 6321
20201 2676 2199 4875
20211 1128 983 2111
2022 1437 1624 3061
Table 4.1. Cod and haddock. Total echo abundance in the Barents Sea winter 1994-2022 (m2 reflecting surface · 103) estimated by StoX. Observations outside main areas A-S are not included.

1 not scaled for uncovered areas

Since 1993 the acoustic values have been split between the two species during the scrutinizing. The values for cod have shown an increasing trend since the late 2000s, with a peak in 2013-2015. Total echo abundance was 40% lower in 2016 compared to 2015 and decreased further from 2016 to 2017, while there was an increase of more than 50% from 2017 to 2018-2019 and then a decrease in 2020 to a level similar to that in 2017. The 2021 echo abundance is the third lowest in the time series, and the lowest observed since 2006 (the lower value in 2007 likely reflects the lack of coverage of the Russian zone and is not directly comparable). The echo abundance increased slightly in 2022, but it is still among the lowest values in the time series.

The values for haddock increased gradually from the end of the 1990s to 2008, decreased gradually to less than one third of the 2008-value in 2016 but increased considerably in 2017 and further in 2018 and 2019, before decreasing in 2020. The 2021 echo abundance is the fourth lowest in the time series, and the lowest observed since 1999. In 2022 the echo abundance increased again, but is still the fourth lowest since 1999.

5 - Distribution and abundance of cod

5.1 - Acoustic estimation

Surveys in the Barents Sea at this time of the year mainly cover the immature part of the cod stock. Most of the mature cod (age 7 and older) have started on their spawning migration southwards out of the investigated area and are therefore to a lesser extent covered. There are indications that a higher proportion than normal spawned along Finnmark in some years, e.g., 2004-2006. Thereby, a higher proportion of spawners might have been covered by the survey in those years. Figure 5.1 shows the spatial distribution of acoustic registrations assigned to cod in 2022. The registrations reflect the general distribution of cod in the central and southwestern Barents Sea. The NASC values in 2022 were low, reflecting the overall low echo abundance.

 

Distribution of acoustic backscatter (m2/nmi2) assigned to cod in 2022. The black lines without yellow circles represent parts of the cruise track where the acoustic backscatter was scrutinized but not assigned to cod. NASC values < 5 was set to zero for this illustration. Circles with red outline represent NASC > 500.
Figure 5.1. COD NASC. Distribution of acoustic backscatter (m2/nmi2 ) assigned to cod in 2022. The black lines without yellow circles represent parts of the cruise track where the acoustic backscatter was scrutinized but not assigned to cod. NASC values < 5 was set to zero for this illustration. Circles with red outline represent NASC > 500.

 

Table 5.1 shows the acoustic indices for each age group by main areas in 2022. 26 % of the 1-year-olds were found in the extended area (N) in 2022 compared to 7 % in 2021. Age 3 cod had the highest percentage of total abundance in area N with 35 %. The time series of total abundance at age (1994-2022) is presented in Table 5.2.

The acoustic estimates have been variable and increasing in later years, with a peak in biomass in 2013, and this may partly be explained by variable and not complete coverage of the distribution area towards north and east in several years. As cod grow older it gets a more south-westerly distribution during winter, so that it “grows into” the covered area with increasing age. This is especially evident for the strong 2004 and 2005 year-classes, which as 6-11-year-olds stand out as the strongest in the time series. The 2019-2020 year-classes were among the lowest in the time series both at age 1 and 2 while the 2021 year-class was moderate at age 1. Table 5.3 shows time series for strata 24-26 (area N) in 2014-2022, which are included in the main time series.

Table 5.4 presents estimated coefficients of variation (CV) for cod age groups 1-14 in 1994-2022. These estimates were obtained by using StoX with a stratified bootstrap routine treating each transect as the primary sampling unit. In addition, a bootstrap routine for all trawl stations by strata was carried out within each run. The estimated CV (Standard Deviation ∙ 100/mean) is estimated from 500 iterations . A CV of 20% or less could be viewed as acceptable in a traditional stock assessment approach if the indices are unbiased (conditional on a catchability model). In 2022 the age groups 1 and 3-7 fall into this category. Values above this indicate higher uncertainty of the estimated index, with reduced information regarding year-class strength. In all years, CVs for age groups older than 10 years are above what could be considered as acceptable. This is to a large degree related to low catch rates resulting in fewer age samples for these age groups (Table 2.2).

Age group Total Biomass (‘000 t)
Area 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
A 24.8 1.13 0.89 2.09 4.47 7.07 8.58 6.08 0.73 0.57 0.82 0.58 0.00 0.00 0.02 57.9 90.8
B 4.27 0.16 1.83 1.41 6.24 6.95 17.5 11.6 4.70 1.13 0.34 0.18 0.08 0.00 0.15 56.5 172.8
C 16.4 0.59 0.71 1.00 1.34 2.10 2.49 2.13 0.50 0.02 0.00 0.05 0.00 0.00 0.06 27.4 27.5
D 178.2 6.28 8.58 17.2 18.7 14.5 5.47 4.15 1.26 0.41 0.20 0.06 0.08 0.00 0.00 255.1 101.2
D'1 9.37 1.46 0.97 2.00 2.44 1.95 1.50 0.70 0.21 0.07 0.04 0.06 0.00 0.00 0.04 20.8 17.6
E 85.7 7.39 1.94 2.45 1.69 2.47 1.46 0.74 0.05 0.03 0.00 0.00 0.00 0.00 0.00 103.9 16.9
S 70.2 12.4 4.10 14.7 12.6 7.86 3.45 1.22 0.20 0.13 0.06 0.01 0.01 0.00 0.00 127.0 51.9
N 135.8 14.0 10.4 12.1 9.16 4.19 2.53 1.13 0.21 0.08 0.04 0.00 0.01 0.00 0.01 189.6 40.6
ABCD 223.7 8.20 12.0 21.7 30.8 30.6 34.0 24.0 7.19 2.13 1.37 0.88 0.16 0.00 0.23 396.9 392.4
AN 524.7 43.4 29.4 53.0 56.7 47.1 42.9 27.8 7.85 2.44 1.51 0.94 0.18 0.00 0.28 838.2 519.4
Table 5.1. COD. Abundance indices (numbers in millions) for the main areas of the Barents Sea from acoustic survey winter 2022 estimated by StoX software. Bootstrap mean estimates.
Age group Total Biomass (‘000 t)4
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
1994 902.64 624.38 323.88 374.47 205.53 70.24 13.00 3.59 2.60 0.71 1.15 0.11 0.13 0.00 0.00 2522.43 1060.26
1995 2175.25 212.29 137.74 139.49 197.08 66.38 15.73 2.43 0.91 0.32 0.48 0.17 0.00 0.00 0.00 2948.27 665.14
1996 1826.33 271.71 99.40 89.62 111.34 82.96 22.17 2.22 0.30 0.10 0.07 0.05 0.10 0.01 0.00 2506.38 504.47
19971 1698.49 565.31 158.57 44.22 49.91 40.91 23.48 5.02 0.84 0.27 0.09 0.00 0.00 0.01 0.00 2587.12 346.39
19981 2523.56 475.15 391.16 189.79 44.87 41.22 27.85 16.06 1.81 0.50 0.04 0.00 0.00 0.00 0.06 3712.07 563.03
1999 364.84 231.51 147.62 130.29 52.03 11.93 6.94 4.13 1.47 0.24 0.01 0.03 0.01 0.00 0.00 951.05 262.81
2000 153.42 262.81 294.83 167.25 145.55 50.75 11.33 4.70 2.75 0.85 0.18 0.11 0.03 0.00 0.00 1094.56 545.52
2001 363.55 51.45 177.44 160.63 80.80 44.47 11.10 1.73 0.46 0.19 0.08 0.00 0.00 0.00 0.01 891.91 435.40
2002 19.22 209.10 61.37 106.23 98.78 52.18 20.07 2.90 0.32 0.52 0.09 0.00 0.00 0.00 0.02 570.8 428.50
2003 1505.00 52.53 306.71 116.80 124.62 116.52 37.69 10.05 1.93 0.31 0.07 0.00 0.08 0.07 0.00 2272.38 755.03
2004 161.20 117.19 33.41 85.21 32.96 28.03 18.14 5.33 1.16 0.31 0.08 0.00 0.01 0.00 0.00 483.03 244.57
2005 499.71 138.66 125.03 33.28 65.94 21.21 15.02 4.95 1.01 0.25 0.05 0.07 0.05 0.03 0.00 905.26 259.70
20062 411.21 157.95 64.77 53.82 18.35 29.52 9.50 4.90 1.28 0.20 0.13 0.30 0.00 0.00 0.00 751.93 227.27
20071 85.13 47.09 58.49 30.40 29.35 9.04 18.07 6.41 2.67 0.53 0.24 0.07 0.00 0.00 0.00 287.49 213.63
2008 50.87 94.20 199.85 288.71 116.17 72.91 21.82 14.43 2.80 0.81 0.04 0.01 0.01 0.00 0.00 862.63 822.87
2009 204.90 25.46 107.83 182.54 138.08 41.48 13.87 4.69 4.32 0.50 0.14 0.02 0.01 0.00 0.00 723.84 536.93
2010 620.25 43.56 22.82 87.98 160.16 154.39 44.56 14.57 3.90 2.89 0.94 0.11 0.12 0.09 0.01 1156.35 885.82
2011 266.00 91.00 40.36 28.32 65.20 106.97 101.80 19.76 6.11 1.70 0.92 0.25 0.15 0.09 0.02 728.65 787.82
20123 496.49 40.23 82.79 49.38 33.77 72.53 132.31 65.59 8.37 4.39 1.21 0.66 0.47 0.04 0.10 988.33 969.09
2013 313.11 89.17 60.55 84.49 72.18 47.75 98.41 130.54 55.32 5.41 4.02 1.30 0.73 0.20 0.07 963.25 1494.33
2014 1758.58 211.04 286.89 124.18 111.14 74.47 39.41 89.89 61.31 22.64 2.56 1.31 0.16 0.05 0.19 2783.82 1437.38
2015 1903.54 211.41 138.71 235.58 128.80 140.36 80.55 35.07 53.80 24.38 7.91 0.80 0.13 0.05 0.01 2961.1 1469.58
2016 240.80 201.89 56.29 76.91 119.38 64.84 50.17 25.80 13.49 17.83 7.35 2.15 0.72 0.22 0.10 877.94 873.17
20173 439.40 73.30 111.54 42.35 44.25 65.30 35.75 24.31 11.97 4.00 2.88 3.15 0.67 0.19 0.11 859.17 680.62
2018 2057.60 280.29 109.03 149.94 53.40 54.93 66.09 34.35 10.78 6.27 1.73 2.25 1.50 0.15 0.23 2828.54 883.80
2019 1437.21 362.38 203.63 125.42 144.06 60.98 34.99 37.86 9.64 3.47 0.55 0.32 0.18 0.28 0.24 2421.21 842.03
20203 92.68 157.92 117.32 117.32 81.36 90.60 42.35 26.57 21.41 6.23 1.75 0.67 0.66 0.51 0.89 758.24 809.18
20213 45.92 28.51 64.86 59.08 55.48 38.54 30.80 12.41 6.32 4.67 2.17 0.29 0.18 0.00 0.21 349.45 400.67
2022 524.71 43.42 29.42 52.98 56.69 47.05 42.94 27.77 7.85 2.44 1.51 0.94 0.18 0.00 0.28 838.17 519.4
Table 5.2. COD. Abundance indices (numbers in millions) from acoustic surveys in the Barents Sea standard area winter 1994-2022 estimated by StoX software. Area N included from 2014 onwards. Bootstrap mean estimates.

1 Indices raised to also represent the Russian EEZ.

2 Not complete coverage in southeast due to restrictions, strata 7 area set to default and strata 13 as in 2005.

3 Indices raised to also represent uncovered parts of the Russian EEZ.

4 1994-2020: bootstrap mean biomass estimated based on relationship between (unraised) numbers-at-age and biomass-at-age from StoX baseline run. From 2021: bootstrap mean biomass estimated directly in StoX; in years with adjustments for lack of coverage it is estimated based on relationship between unraised bootstrap mean numbers-at-age and unraised bootstrap mean biomass-at-age.

Age group Total Biomass (‘000 t)
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
2014 1112.50 53.97 54.53 11.67 14.62 7.31 2.26 4.73 2.98 0.27 0.02 0.00 0.00 0.00 0.00 1264.87 103.44
2015 589.67 88.32 25.22 49.00 12.68 11.24 5.34 1.08 3.40 1.16 0.77 0.05 0.00 0.00 0.00 787.93 122.36
2016 104.90 84.60 17.95 14.58 16.83 2.47 2.94 1.86 0.30 0.67 0.17 0.02 0.01 0.00 0.00 247.30 60.15
2017 31.09 28.70 26.54 5.44 5.68 4.13 1.54 0.65 0.24 0.05 0.28 0.04 0.00 0.00 0.00 104.37 40.15
2018 514.18 50.59 16.17 16.74 6.96 4.35 8.64 0.99 0.76 0.25 0.08 0.12 0.01 0.00 0.00 619.85 76.08
2019 371.39 75.30 20.87 27.74 20.56 7.98 3.63 5.27 0.42 0.44 0.14 0.04 0.01 0.03 0.00 533.82 112.10
2020 12.66 13.01 16.05 11.60 12.75 7.53 3.10 1.87 2.67 0.44 0.25 0.09 0.06 0.00 0.08 82.15 71.84
2021 3.35 1.85 4.11 6.72 4.13 3.70 1.61 0.45 0.20 0.21 0.01 0.01 0.00 0.00 0.01 26.36 24.23
2022 135.8 14.0 10.4 12.1 9.16 4.19 2.53 1.13 0.21 0.08 0.04 0.00 0.01 0.00 0.01 189.6 40.6
Table 5.3. COD. Abundance indices (numbers in millions) for new strata 24-26 from acoustic surveys in the Barents Sea winter 2014-2022 estimated by StoX software. 2014-2020: baseline estimates, from 2021: bootstrap mean estimates.
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1994 30 41 29 12 7 10 13 19 20 29 29 69 89 -
1995 14 24 15 9 7 8 12 23 26 35 54 50 - -
1996 11 15 14 10 10 11 14 16 29 43 58 54 100 110
19971 33 29 14 11 10 10 8 13 22 54 63 - - 129
19981 23 18 11 9 10 8 8 11 22 36 45 - 101 -
1999 22 23 17 15 10 11 11 13 25 58 114 121 107 -
2000 31 26 17 10 7 10 17 21 22 42 72 68 110 -
2001 13 15 11 9 10 9 13 22 32 36 78 - - -
2002 18 16 10 6 7 10 15 17 32 78 73 - - -
2003 26 31 15 13 8 8 13 17 20 40 59 - 99 94
2004 18 16 13 10 10 10 9 13 16 45 58 95 125 -
2005 26 49 19 14 14 14 12 20 26 24 62 90 49 91
20062 24 14 11 8 8 10 16 18 19 37 61 66 - -
20071 27 24 14 14 11 17 21 24 27 36 42 44 92 -
2008 18 24 15 16 13 10 16 14 20 44 75 65 100 -
2009 21 20 26 22 18 17 13 14 19 32 45 71 112 -
2010 36 17 19 25 17 12 11 13 17 22 28 86 74 70
2011 13 27 12 11 11 10 9 15 28 29 35 39 66 86
20122 36 14 53 11 19 19 17 13 19 35 33 55 52 81
2013 15 21 13 9 11 11 14 11 18 35 44 55 66 108
2014 15 10 11 10 13 8 11 11 14 21 30 53 59 96
2015 27 22 15 15 10 14 18 21 19 29 48 55 63 70
2016 36 20 13 13 11 15 17 16 23 23 32 46 55 87
20172 15 19 12 11 10 8 11 14 21 22 19 25 31 58
2018 11 9 9 9 9 8 8 13 15 24 24 33 53 51
2019 12 12 8 7 6 11 12 10 14 23 32 55 49 60
20202 15 15 10 7 10 11 15 16 18 23 29 38 31 38
20212 32 42 34 21 13 13 17 16 20 20 29 44 69 175
2022 20 25 20 17 11 11 19 21 31 36 48 52 74 -
Table 5.4 . COD. Estimates of coefficients of variation (%) for acoustic abundance indices. Barents Sea standard area winter 1994-2022.

1 Russian EEZ not covered

2 Russian EEZ partly covered

5.2 - Swept area estimation

Figures 5.2 - 5.5 show the geographic distribution of bottom trawl catch rates (number of fish per NM2 ), for cod size groups < 20 cm, 20-34 cm, 35-49 cm and ≥ 50 cm. Usually, a high proportion of the smallest cod (less than 35 cm) are found in the eastern part of the survey area within the Russian EEZ and near the northern borders of the standard strata system (strata 1-23). While this general pattern was still there in 2022, the 20-34 cm cod was nearly absent from the southern and south-eastern areas (Fig. 5.3). Catch rates of medium and large sized cod (35-50+ cm) were particularly low in the central Barents Sea (Figs 5.4-5.5). The highest catch rates of large cod are usually found along the Norwegian coast and around Svalbard and the ice edge in the north, but in 2022 there were relatively lower catch rates in the south (Fig. 5.5).

 

COD < 20 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 5.2. COD < 20 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2 ). Black crosses indicate zero catches and the stippled line the ice edge. Data source for the ice cover: https://cryo.met.no/archive/ice-service/icecharts/quicklooks/2022/

 

 

COD 20-34 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 5.3. COD 20-34 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

 

COD 35-49 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 5.4. COD 35-49 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm 2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

 

COD ≥ 50 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 5.5. COD ≥ 50 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm 2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

Table 5.5 presents abundance indices by main areas and age, and the full time series 1994-2022 is shown in Table 5.6. The bottom trawl indices have fluctuated somewhat for the same reasons as the acoustic indices, and the 2004 and 2005 year-classes stand out as the strongest in the time series. The 2009, 2011 and 2014 year-classes seemed to be strong as 1-year olds but have later been reduced to average level or below. The year-classes 2017 and 2018 also seemed strong at age one but are more average as 2- and 3-year-olds. The 2019-2020 year-classes were among the lowest in the time series both at age 1 and 2 while the 2021 year-class was moderate at age 1. A considerable number of cod was found in the extended survey area N (Table 5.7), which from 2021 was included in the official indices used for stock assessment. Looking at total estimates, about 23% of cod by numbers and about 16% by biomass were found in this area in 2022. Tables 5.7 present swept area abundance indices by age for area N in 2014-2022. As in the previous years, fair amounts of cod were also observed northeast of the extended area, i.e., north of Svalbard outside of the survey stratification.

Table 5.8 presents estimated coefficients of variation (CV) for cod age groups 1-15 in 1994-2021. In 2022, age groups 1-2 and 5-9 have CVs below or equal to 20 %. Values above this indicate higher uncertainty of the estimated index, with reduced information regarding year-class strength. In all years, CVs for age groups older than 10 years are above what could be considered as acceptable. This is to a large degree related to low catch rates resulting in fewer age samples for these age groups (Table 2.2).

Age group Total Biomass (‘000 t)
Area 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
A 20.5 0.98 0.75 1.70 3.24 5.38 3.54 4.29 0.55 0.46 0.37 0.20 0.00 0.00 0.02 41.9 53.2
B 0.92 0.06 0.42 0.30 2.05 1.44 6.89 3.62 0.92 0.21 0.05 0.05 0.01 0.00 0.05 17.0 52.0
C 6.15 0.22 0.28 0.31 0.57 0.63 0.84 0.80 0.18 0.00 0.00 0.02 0.00 0.00 0.02 10.0 9.74
D 218.1 9.59 11.2 21.8 25.6 20.7 7.58 6.26 1.79 0.52 0.24 0.10 0.12 0.00 0.00 323.7 140.9
D'1 42.8 8.13 4.46 7.38 8.40 10.6 13.6 3.91 1.21 0.69 1.20 1.11 0.00 0.00 0.77 104.1 147.1
E 128.7 12.5 2.67 4.15 2.20 5.14 0.67 5.75 0.04 0.04 0.00 0.00 0.00 0.00 0.00 161.8 40.8
S 91.8 16.1 16.3 30.8 23.0 12.75 5.20 1.84 0.42 0.13 0.07 0.02 0.01 0.00 0.00 198.6 90.7
N 158.9 18.1 15.8 22.2 21.5 9.86 6.33 3.96 0.58 0.26 0.15 0.00 0.02 0.00 0.03 257.8 99.7
ABCD 245.6 10.8 12.7 24.1 31.5 28.2 18.9 15.0 3.4 1.2 0.7 0.4 0.1 0.00 0.10 392.6 255.7
AN 667.8 65.6 52.0 88.7 86.6 66.5 44.6 30.4 5.7 2.3 2.1 1.5 0.2 0.00 0.90 1114.9 634.0
Table 5.5. COD. Abundance indices from bottom trawl hauls for main areas of the Barents Sea winter 2022 (numbers in millions). Bootstrap mean estimates.
Age group Total Biomass (‘000 t)
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
1994 1043.78 556.68 293.92 307.04 153.33 45.72 7.95 2.61 1.48 0.55 0.55 0.08 0.05 0 0 2413.74 763.41
1995 5356.43 541.25 282.84 242.36 251.01 76.42 17.98 2.42 1.07 0.50 0.61 0.19 0 0 0 6773.08 937.79
1996 5899.23 791.62 163.08 117.43 138.59 108.88 24.43 2.64 0.37 0.17 0.12 0.07 0.07 0.02 0 7246.72 718.00
19971 5044.09 1422.92 317.99 68.44 74.26 59.99 26.67 4.85 0.64 0.91 0.08 0 0 0 0 7020.84 558.85
19981 2490.54 496.48 355.10 166.94 31.67 26.15 17.52 8.16 0.79 0.52 0.04 0 0 0 0.04 3593.95 432.77
1999 473.04 350.21 188.48 180.75 61.39 12.71 6.81 5.14 1.01 0.26 0.02 0.04 0.02 0 0 1279.88 322.68
2000 128.57 242.33 245.81 130.03 111.73 26.75 4.56 1.84 1.21 0.33 0.10 0.03 0.02 0 0 893.31 363.23
2001 712.77 78.03 182.79 195.11 82.90 37.96 9.45 1.17 0.44 0.19 0.04 0 0 0 0.01 1300.86 436.57
2002 34.11 418.73 118.36 137.56 108.95 45.79 14.40 2.20 0.32 0.18 0.05 0 0 0 0.02 880.67 447.43
2003 3022.23 65.78 376.70 126.31 93.93 66.88 17.50 4.67 1.02 0.17 0.04 0 0.02 0.02 0 3775.27 546.13
2004 322.87 242.94 63.88 184.62 53.46 43.24 30.59 6.85 1.65 0.28 0.07 0.01 0.01 0 0 950.47 415.07
2005 853.43 216.67 248.88 55.06 102.97 22.38 16.36 3.81 0.92 0.30 0.04 0.02 0.04 0.04 0 1520.92 359.76
20062 674.21 289.39 116.49 115.38 28.32 43.42 13.72 5.24 1.36 0.24 0.18 0.18 0 0 0 1288.13 334.94
20071 594.69 369.74 361.13 127.73 68.51 13.65 23.60 6.82 2.30 0.41 0.11 0.10 0 0 0 1568.79 444.84
2008 68.83 101.96 194.37 300.59 111.90 40.24 17.34 8.11 1.79 0.36 0.03 0.02 0.01 0 0 845.55 686.98
2009 389.48 35.59 126.28 196.70 220.23 60.69 17.90 9.02 5.24 0.51 0.17 0.03 0.04 0 0 1061.88 757.32
2010 1027.59 95.14 36.81 114.25 154.80 144.50 39.56 11.24 3.67 1.60 0.58 0.04 0.02 0.04 0.02 1629.86 827.36
2011 617.18 225.81 85.40 50.37 129.70 138.66 103.51 16.37 4.36 1.20 0.82 0.19 0.14 0.04 0.02 1373.77 891.44
20123 702.97 100.30 75.72 64.59 33.71 90.69 132.58 48.61 9.02 2.26 0.88 0.55 0.44 0.07 0.05 1262.44 879.93
2013 435.72 142.96 68.84 114.09 63.18 40.43 64.54 76.38 33.52 2.22 2.87 0.40 0.35 0.06 0.03 1045.59 951.73
2014 1245.71 191.48 226.85 93.79 88.59 56.39 32.74 53.05 36.19 9.81 1.01 0.95 0.15 0.02 0.08 2036.81 897.87
2015 1642.00 342.76 144.07 228.25 147.29 113.53 74.43 29.22 53.51 18.08 3.38 0.75 0.12 0.07 0.04 2797.50 1338.73
2016 312.16 305.57 99.37 135.48 188.31 113.47 72.33 28.56 13.17 16.06 6.77 0.97 0.52 0.17 0.14 1293.05 1085.06
20173 644.51 128.92 179.25 62.15 84.54 90.16 37.82 26.33 8.18 3.26 2.61 3.70 0.58 0.17 0.06 1272.24 753.67
2018 2714.35 500.69 139.41 184.78 61.81 64.17 73.88 25.88 9.28 5.87 1.29 2.46 1.23 0.13 0.37 3785.60 908.45
2019 1790.57 559.44 281.57 179.15 221.90 79.65 32.96 38.31 8.15 2.62 0.54 0.24 0.16 0.18 0.12 3195.56 974.96
20203 164.75 273.82 237.73 160.24 131.56 114.88 49.83 24.26 20.44 4.53 1.66 0.93 0.51 0.26 0.73 1186.13 857.96
20213 80.88 34.87 111.50 119.35 112.31 54.28 37.98 13.57 7.27 3.53 1.25 0.42 0.25 0.04 0.32 577.83 528.35
2022 667.8 65.6 52.0 88.7 86.6 66.5 44.6 30.4 5.70 2.29 2.08 1.49 0.16 0.00 0.90 1114.9 634.0
Table 5.6. COD. Abundance indices (numbers in millions) from bottom trawl surveys in the Barents Sea winter 1994-2022. Area N included from 2014 onwards. Bootstrap mean estimates.

1 Indices raised to also represent the Russian EEZ. 2 Not complete coverage in southeast due to restrictions, strata 7 area set to default and strata 13 as in 2005

3 Indices raised to also represent uncovered parts of the Russian EEZ.

4 1994-2020: bootstrap mean biomass estimated based on relationship between (unraised) numbers-at-age and biomass-at-age from StoX baseline run. From 2021: bootstrap mean biomass estimated directly in StoX; in years with adjustments for lack of coverage it is estimated based on relationship between unraised bootstrap mean numbers-at-age and unraised bootstrap mean biomass-at-age

Age group Total Biomass (‘000 t)
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
2014 713.08 77.53 42.89 18.72 15.38 9.93 2.90 5.31 3.65 0.55 0.06 0.01 0.00 0.00 0.00 890.00 117.15
2015 403.27 85.44 26.44 46.50 20.73 11.77 5.27 1.82 2.47 1.44 0.45 0.06 0.00 0.00 0.00 605.64 129.79
2016 101.28 92.79 27.21 24.25 28.17 9.40 5.58 2.52 0.61 0.96 0.35 0.05 0.02 0.00 0.00 293.19 109.39
2017 182.91 49.50 60.34 27.67 28.94 31.41 10.26 3.29 0.60 0.26 0.33 0.08 0.00 0.00 1.72 397.32 187.18
2018 1010.90 115.27 29.03 42.62 13.37 11.59 14.39 4.05 1.55 0.40 0.19 0.24 0.03 0.00 0.00 1243.61 170.48
2019 493.52 119.15 40.37 33.55 42.75 12.63 6.88 8.39 1.43 0.61 0.14 0.08 0.02 0.06 0.00 759.60 190.84
2020 25.44 30.50 36.58 33.77 22.46 21.42 8.16 4.32 3.99 0.85 0.44 0.06 0.11 0.00 0.09 188.20 162.34
2021 31.98 12.50 22.74 32.50 26.64 14.80 7.51 1.66 1.13 0.86 0.04 0.08 0.00 0.00 0.02 152.45 115.76
2022 158.91 18.08 15.83 22.22 21.53 9.86 6.33 3.96 0.58 0.26 0.15 0.00 0.02 NA 0.03 257.76 99.69
Table 5.7. COD. Abundance indices (numbers in millions) for new strata 24-26 from bottom trawl surveys in the Barents Sea winter 2014-2022. Bootstrap mean estimates.
Age group
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
1994 7 15 10 10 10 9 13 24 23 25 18 72 69 - -
1995 8 14 11 12 10 10 12 23 33 27 42 39 - - -
1996 7 12 19 10 12 9 13 13 25 40 50 39 48 92 -
19971 27 29 17 14 13 10 9 15 21 56 70 - - - -
19981 8 12 15 11 11 11 8 10 17 48 61 - 95 - 68
1999 18 28 17 14 9 10 14 29 22 62 106 95 91 - -
2000 12 18 15 8 9 10 12 11 15 32 55 65 84 - -
2001 11 15 17 14 10 11 16 23 28 36 57 - - - 96
2002 13 23 24 7 9 13 9 14 26 40 63 - - - 93
2003 25 33 26 19 8 7 10 12 17 40 55 - 71 69 -
2004 12 13 19 14 10 12 14 12 14 36 40 106 101 - -
2005 9 18 27 20 18 14 11 10 16 23 61 66 49 94 -
20062 12 13 14 27 17 13 21 12 17 27 55 63 - - -
20071 25 21 16 25 7 10 10 14 19 19 34 47 84 - -
2008 9 16 16 23 31 9 37 14 25 24 70 83 99 - -
2009 10 10 16 11 19 13 16 23 22 31 33 61 91 - -
2010 33 10 13 19 13 10 21 11 22 21 25 71 57 60 -
2011 6 24 11 15 16 10 9 10 26 19 48 36 58 64 99
20122 9 14 13 12 15 20 20 12 24 19 23 39 52 76 100
2013 10 19 14 17 12 10 12 10 17 21 55 34 43 102 94
2014 11 9 10 11 11 7 16 12 11 19 26 33 61 117 68
2015 7 19 12 13 15 16 27 21 40 16 21 28 74 71 82
2016 9 11 15 11 8 17 19 11 15 25 20 33 31 53 52
20172 10 11 12 14 26 15 19 23 11 18 20 26 43 37 96
2018 6 14 7 9 8 12 8 12 12 29 20 34 48 46 48
2019 8 8 9 9 16 16 12 8 14 15 24 35 40 35 82
20202 14 10 13 16 11 11 12 10 12 14 21 52 29 39 30
20212 15 10 16 11 10 12 10 16 15 13 24 38 68 91 46
2022 7 12 22 21 15 10 16 18 15 27 58 72 41 - 91
Table 5.8. COD. Estimates of coefficients of variation (%) for swept area abundance indices. Barents Sea standard area winter 1994-2022.

1Russian EEZ not covered

2Russian EEZ partly covered

5.3 - Survey mortalities

Table 5.9 gives the time series of survey-based mortalities (natural log ratios between survey indices of the same year-class in two successive years) for the acoustic and swept area indices since 1994. These mortalities are influenced by natural and fishing mortality, age reading errors, and the catchability and availability (coverage) at age for the survey. In the period 1994-1999 there was an increasing trend in the survey mortalities. Most later surveys show lower mortalities, but there are some fluctuations for the same reasons as mentioned for the acoustic and swept area indices. Presumably the mortality of the youngest age groups (ages 1-3) is mainly caused by predation, while for the older age groups the fishery is the main cause. Although the survey mortalities are noisy, the mortalities for age 4 and older correspond well with the strong decrease in fishing mortality around 2007 in the stock assessment. The low survey mortalities in the 2010s, even with “impossible” negative values, could partly be caused by fish gradually “growing into” the covered area at increasing age. 2019-2020 and 2020-2021 estimates suggest higher survey mortalities than in previous years, while mortality decreased for most age groups in 2021-2022.

  Age
Year 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9
  Acoustic investigations
1994-95 1.45 1.51 0.84 0.64 1.13 1.50 1.68 1.37
1995-96 2.08 0.76 0.43 0.23 0.87 1.10 1.96 2.09
1996-97 1.17 0.54 0.81 0.59 1.00 1.26 1.49 0.97
1997-98 1.27 0.37 -0.18 -0.01 0.19 0.38 0.38 1.02
1998-99 2.39 1.17 1.10 1.29 1.32 1.78 1.91 2.39
1999-00 0.33 -0.24 -0.12 -0.11 0.02 0.05 0.39 0.41
2000-01 1.09 0.39 0.61 0.73 1.19 1.52 1.88 2.32
2001-02 0.55 -0.18 0.51 0.49 0.44 0.80 1.34 1.69
2002-03 -1.01 -0.38 -0.64 -0.16 -0.17 0.33 0.69 0.41
2003-04 2.55 0.45 1.28 1.27 1.49 1.86 1.96 2.16
2004-05 0.15 -0.06 0.00 0.26 0.44 0.62 1.30 1.66
2005-06 1.15 0.76 0.84 0.60 0.80 0.80 1.12 1.35
2006-07 2.17 0.99 0.76 0.61 0.71 0.49 0.39 0.61
2007-08 -0.10 -1.45 -1.60 -1.34 -0.91 -0.88 0.22 0.83
2008-09 0.69 -0.14 0.09 0.74 1.03 1.66 1.54 1.21
2009-10 1.55 0.11 0.20 0.13 -0.11 -0.07 -0.05 0.18
2010-11 1.92 0.08 -0.22 0.30 0.40 0.42 0.81 0.87
2011-12 1.89 0.09 -0.20 -0.18 -0.11 -0.21 0.44 0.86
2012-13 1.72 -0.41 -0.02 -0.38 -0.35 -0.31 0.01 0.17
2013-14 0.39 -1.17 -0.72 -0.27 -0.03 0.19 0.09 0.76
2014-15 2.12 0.42 0.20 -0.04 -0.23 -0.08 0.12 0.51
2015-16 2.24 1.32 0.59 0.68 0.69 1.03 1.14 0.96
2016-17 1.19 0.59 0.28 0.55 0.60 0.60 0.72 0.77
2017-18 0.45 -0.40 -0.30 -0.23 -0.22 -0.01 0.04 0.81
2018-19 1.74 0.32 -0.14 0.04 -0.13 0.45 0.56 1.27
2019-20 2.21 1.13 0.55 0.43 0.46 0.36 0.28 0.57
2020-21 1.41 0.93 0.73 0.79 0.77 1.11 1.26 1.54
2021-22 0.06 -0.03 0.20 0.04 0.16 -0.11 0.10 0.46
  Bottom trawl investigations
1994-95 0.66 0.68 0.19 0.20 0.70 0.93 1.19 0.89
1995-96 1.91 1.20 0.88 0.56 0.84 1.14 1.92 1.88
1996-97 1.42 0.91 0.87 0.46 0.84 1.41 1.62 1.42
1997-98 2.32 1.39 0.64 0.77 1.04 1.23 1.18 1.81
1998-99 1.96 0.97 0.68 1.00 0.91 1.35 1.23 2.09
1999-00 0.67 0.35 0.37 0.48 0.83 1.03 1.31 1.45
2000-01 0.50 0.28 0.23 0.45 1.08 1.04 1.36 1.43
2001-02 0.53 -0.42 0.28 0.58 0.59 0.97 1.46 1.30
2002-03 -0.66 0.11 -0.07 0.38 0.49 0.96 1.13 0.77
2003-04 2.52 0.03 0.71 0.86 0.78 0.78 0.94 1.04
2004-05 0.40 -0.02 0.15 0.58 0.87 0.97 2.08 2.01
2005-06 1.08 0.62 0.77 0.66 0.86 0.49 1.14 1.03
2006-07 0.60 -0.22 -0.09 0.52 0.73 0.61 0.70 0.82
2007-08 1.76 0.64 0.18 0.13 0.53 -0.24 1.07 1.34
2008-09 0.66 -0.21 -0.01 0.31 0.61 0.81 0.65 0.44
2009-10 1.41 -0.03 0.10 0.24 0.42 0.43 0.47 0.90
2010-11 1.52 0.11 -0.31 -0.13 0.11 0.33 0.88 0.95
2011-12 1.82 1.09 0.28 0.40 0.36 0.04 0.76 0.60
2012-13 1.59 0.38 -0.41 0.02 -0.18 0.34 0.55 0.37
2013-14 0.82 -0.46 -0.31 0.25 0.11 0.21 0.20 0.75
2014-15 1.29 0.28 -0.01 -0.45 -0.25 -0.28 0.11 -0.01
2015-16 1.68 1.24 0.06 0.19 0.26 0.45 0.96 0.80
2016-17 0.88 0.53 0.47 0.47 0.74 1.10 1.01 1.25
2017-18 0.25 -0.08 -0.03 0.01 0.28 0.20 0.38 1.04
2018-19 1.58 0.58 -0.25 -0.18 -0.25 0.67 0.66 1.16
2019-20 1.88 0.86 0.56 0.31 0.66 0.47 0.31 0.63
2020-21 1.55 0.90 0.69 0.36 0.89 1.11 1.30 1.21
2021-22 0.21 -0.40 0.23 0.32 0.52 0.20 0.22 0.87
Table 5.9. COD. Survey mortality from surveys in the Barents Sea standard area winter 1994-2022.

5.4 - Growth and maturity

Tables 5.10 and 5.11 present the time series for mean length and mean weight at age for the standard area. There have previously only been moderate fluctuations, but with a decreasing trend for older fish (8+) in later years. However, in 2020-2021, both length and weight at age was considerably reduced for several age groups, with length at age 4 and 5 and weight at age 4, 5, 6 and 8 in 2021 being the lowest observed in the time series. Growth improved somewhat in 2022, but for age groups 1 and 4-9, weight at age is below average in 2022. The reduced weights in the latest years are reflected in the annual weight increments, which for ages 1-5 in from 2019-2002 and 2020-2021 were at or near the lowest observed while growth between 2021 and 2022 was around average for most ages (Table 5.12).

The proportion mature at age is presented in Table 5.13. Since 2010, the proportion mature at ages 6-8 has declined but has in recent years stabilized. Low values were, however, observed for ages 6 and 9 in 2022.

The degree of coverage of the Russian EEZ may also influence the biological parameters, as body size tends to decrease towards the northeast in the survey area. In addition, length, weight, and maturity at age of older ages has higher uncertainty due to fewer samples (c.f. table 2.2).

Age/ Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1994 11.3 17.9 30.2 44.6 55.2 65.7 73.9 78.9 87.4 97.2 97.6 104.7 + -
1995 12.2 18.1 29.0 42.2 53.9 63.9 75.4 80.4 85.9 99.1 90.1 109.0 - -
1996 12.1 18.8 28.8 40.5 49.4 60.9 71.8 85.1 92.4 94.9 96.1 104.2 103.9 +
19971 10.8 16.9 29.7 41.0 50.6 59.4 69.6 81.2 92.3 80.4 + - - -
19981 10.5 17.8 30.8 40.9 50.9 58.5 67.7 76.7 87.2 103.0 111.4 - + -
1999 12.0 18.4 29.0 40.0 50.4 59.4 70.4 78.4 88.5 87.6 + + + -
2000 12.8 20.7 28.4 39.7 51.5 61.4 70.4 76.3 84.9 84.3 100.0 + + -
2001 11.6 22.6 33.0 41.2 52.2 63.3 70.4 78.3 86.0 95.7 104.7 - - -
2002 12.0 19.6 28.9 43.6 52.1 61.9 71.4 79.5 91.2 89.7 103.7 - - -
2003 11.4 18.1 29.1 39.7 53.4 61.7 70.6 80.8 89.1 90.1 105.4 - + +
2004 10.6 18.4 31.7 40.6 51.7 61.6 68.6 79.7 90.9 90.4 92.2 + + -
2005 11.2 18.3 29.5 43.4 51.1 60.4 71.0 79.6 89.0 96.4 109.3 + 129.6 +
20062 12.0 19.4 30.9 42.1 53.8 60.3 66.7 76.7 84.9 98.9 95.4 84.9 - -
20071 13.2 20.7 29.6 41.1 52.8 62.5 70.4 78.2 87.5 92.7 101.8 121.6 + -
2008 12.1 22.3 33.0 43.2 51.8 64.0 69.9 81.3 88.7 95.3 + + + -
2009 11.2 21.1 32.1 42.6 53.2 61.9 76.6 81.8 89.5 97.8 99.5 + + -
2010 11.2 18.4 31.4 42.7 52.4 60.7 70.5 80.4 88.8 96.3 102.2 + + 126.0
2011 11.9 19.5 29.4 41.9 51.0 60.7 68.1 78.3 86.1 95.4 102.2 110.4 114.3 +
20122 10.6 18.4 29.7 41.0 52.4 58.1 66.5 75.6 86.0 91.8 105.9 114.0 119.0 +
2013 11.2 19.3 31.1 41.1 51.7 62.0 69.7 76.5 81.2 95.3 93.7 110.7 110.8 +
2014 9.7 17.1 29.5 40.5 52.0 59.6 70.2 76.8 81.8 87.1 97.4 98.9 107.8 +
2015 10.5 15.9 30.0 40.3 51.1 60.2 68.8 77.5 81.2 88.7 94.0 101.9 127.5 +
2016 12.2 18.3 27.7 40.6 49.8 60.5 68.3 76.6 85.5 86.5 90.5 94.1 112.0 122.5
20172 12.3 22.2 31.2 42.5 51.2 60.5 69.6 75.5 85.2 90.9 96.0 92.6 108.6 108.7
2018 11.2 19.1 32.7 42.4 51.2 61.6 69.0 77.5 83.4 87.6 97.0 99.3 101.8 106.8
2019 11.7 17.5 31.2 42.4 51.0 59.6 69.7 77.0 84.1 87.1 99.3 103.4 104.6 109.8
20202 12.0 17.5 25.5 39.5 50.2 58.6 66.7 74.8 83.0 90.0 93.9 92.4 111.2 113.9
20212 11.6 19.9 26.5 37.4 48.0 58.5 66.7 74.9 84.0 91.7 97.7 102.1 105.8 +
2022 10.8 20.4 32.4 39.1 49.3 58.4 68.7 75.3 84.1 92.5 98.2 102.6 113.2 -
Table 5.10 COD. Mean length (cm) at age from bottom trawl surveys in the Barents Sea standard area winter 1994-2022. Bootstrap mean estimates. “+” indicates few samples (< 3), while “–“ indicates no samples. Lengths are not adjusted for incomplete coverage.

1 Russian EEZ not covered

2 Russian EEZ partly covered

Age/ Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1994 13 56 262 796 1470 2386 3481 4603 6777 8195 8516 13972 + -
1995 15 54 240 658 1336 2207 3570 4715 5712 8816 6817 12331 - -
1996 15 62 232 627 1084 1980 3343 5514 7722 8873 9613 12865 12556 +
19971 13 52 230 638 1175 1797 2931 4875 7529 5739 + - - -
19981 11 52 280 635 1182 1728 2588 4026 6076 11257 14391 - + -
1999 14 59 231 592 1178 1829 2991 4128 6321 7342 + + + -
2000 16 74 210 558 1210 1963 3036 3867 5401 6154 10023 + + -
2001 14 106 336 646 1288 2233 3088 4439 5732 8442 11429 - - -
2002 14 67 238 747 1229 2063 3199 4578 7525 6598 12292 - - -
2003 13 61 234 597 1316 2014 2989 4715 6517 7500 12812 - + +
2004 11 59 275 608 1143 1947 2623 4137 6673 7368 8109 + + -
2005 13 61 246 723 1146 1866 2949 4226 6436 8646 12537 + 24221 -
20062 13 69 280 669 1420 1970 2641 4260 5914 10179 9439 8328 - -
20071 19 73 235 639 1302 2190 3039 4411 6394 8056 10826 20104 + -
2008 15 90 335 798 1399 2442 3235 5210 6981 9641 + + + -
2009 13 83 294 704 1302 2065 4067 5087 6874 9460 9511 + + -
2010 12 64 304 700 1296 2033 3162 4743 6562 8984 10315 + + 22766
2011 15 66 246 668 1131 1940 2726 4013 5969 8275 10309 13159 14868 +
20122 13 62 252 609 1276 1681 2489 3764 5920 7809 12199 15006 17582 +
2013 11 65 269 602 1208 2055 2809 3843 4822 8447 9101 15108 14743 +
2014 8 50 246 603 1226 1780 2866 3930 4927 6203 8570 9566 12239 +
2015 10 44 242 602 1221 1929 2741 4043 4804 6817 7759 11544 21652 +
2016 13 53 200 593 1049 1928 2674 3830 5540 6129 7110 8272 15256 21945
20172 15 102 292 720 1178 1972 3056 3962 5901 7429 9301 8599 12958 14894
2018 12 69 320 688 1228 2062 2803 4154 5409 6632 9156 10510 11810 12443
2019 12 48 273 685 1164 1870 2916 3974 5394 6068 9637 11507 12371 13993
20202 14 44 153 548 1077 1692 2476 3625 5074 6758 8040 8107 14892 15793
20212 14 68 164 462 910 1682 2484 3620 5379 7160 9313 10923 12410 +
2022 11 77 311 535 1052 1716 2885 3855 5321 7751 9538 11432 14940 -
Table 5.11. COD. Mean weight (g) at age from bottom trawl surveys in the Barents Sea standard area winter 1994-2022. Bootstrap mean estimates. “+” indicates few samples (< 3), while “–“ indicates no samples. Weights are not adjusted for incomplete coverage.

1 Russian EEZ not covered

2 Russian EEZ partly covered

Year\Age 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10
1994-95 41 184 396 540 737 1184 1234 1109 2039
1995-96 47 178 387 426 644 1136 1944 3007 3161
1996-97 37 168 406 548 713 951 1532 2015 -1983
1997-98 39 228 405 544 553 791 1095 1201 3728
1998-99 48 179 312 543 647 1263 1540 2295 1266
1999-00 60 151 327 618 785 1207 876 1273 -167
2000-01 90 262 436 730 1023 1125 1403 1865 3041
2001-02 53 132 411 583 775 966 1490 3086 866
2002-03 47 167 359 569 785 926 1516 1939 -25
2003-04 46 214 374 546 631 609 1148 1958 851
2004-05 50 187 448 538 723 1002 1603 2299 1973
2005-06 56 219 423 697 824 775 1311 1688 3743
2006-07 60 166 359 633 770 1069 1770 2134 2142
2007-08 71 262 563 760 1140 1045 2171 2570 3247
2008-09 68 204 369 504 666 1625 1852 1664 2479
2009-10 51 221 406 592 731 1097 676 1475 2110
2010-11 54 182 364 431 644 693 851 1226 1713
2011-12 47 186 363 608 550 549 1038 1907 1840
2012-13 52 207 350 599 779 1128 1354 1058 2527
2013-14 39 181 334 624 572 811 1121 1084 1381
2014-15 36 192 356 618 703 961 1177 874 1890
2015-16 43 156 351 447 707 745 1089 1497 1325
2016-17 89 239 520 585 923 1128 1288 2071 1889
2017-18 54 218 396 508 884 831 1098 1447 731
2018-19 36 204 365 476 642 854 1171 1240 659
2019-20 32 105 275 392 528 606 709 1100 1364
2020-21 54 120 309 362 605 792 1144 1754 2086
2021-22 63 243 371 590 806 1203 1371 1701 2372
Table 5.12. COD. Yearly weight increment (g) from bottom trawl surveys in the Barents Sea standard area winter 1994-2022.
Age/ Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1994 0.00 0.00 0.00 0.00 0.06 0.14 0.31 0.71 0.92 1.00 0.83 1.00 + -
1995 0.00 0.00 0.00 0.01 0.05 0.26 0.32 0.51 0.85 0.91 1.00 1.00 - -
1996 0.00 0.00 0.00 0.00 0.01 0.16 0.33 0.51 1.00 1.00 1.00 1.00 1.00 +
1997 0.00 0.00 0.00 0.00 0.01 0.08 0.38 0.80 1.00 0.83 + - - -
1998 0.00 0.00 0.00 0.01 0.04 0.18 0.33 0.64 0.84 1.00 - + - -
1999 - 0.00 0.00 0.00 0.01 0.12 0.37 0.70 0.88 + + + - +
2000 0.00 0.00 0.00 0.00 0.05 0.28 0.85 0.86 1.00 1.00 + + - +
2001 0.00 0.00 0.00 0.01 0.05 0.27 0.43 0.70 0.91 1.00 - - - -
2002 - 0.00 0.00 0.01 0.04 0.29 0.47 0.56 0.87 1.00 - - - -
2003 - 0.00 0.00 0.00 0.05 0.21 0.40 0.69 0.94 1.00 - + + -
2004 - 0.00 0.00 0.01 0.05 0.25 0.53 0.72 0.87 0.88 + + - +
2005 0.00 0.00 0.00 0.00 0.04 0.18 0.49 0.80 0.92 1.00 1.00 + 1.00 -
2006 0.00 0.00 0.00 0.03 0.05 0.20 0.39 0.74 0.72 1.00 1.00 1.00 - -
2007 0.00 0.00 0.00 0.01 0.05 0.33 0.57 0.84 0.98 1.00 1.00 1.00 + -
2008 0.00 0.00 0.01 0.01 0.12 0.32 0.54 0.74 0.82 1.00 1.00 + + -
2009 0.00 0.00 0.00 0.00 0.08 0.25 0.49 0.64 0.91 0.96 0.86 + + -
2010 - 0.00 0.01 0.01 0.10 0.37 0.50 0.79 0.89 0.95 0.93 + + 1.00
2011 0.00 0.00 0.00 0.00 0.03 0.22 0.43 0.54 0.84 0.88 1.00 1.00 1.00 +
2012 0.00 0.00 0.00 0.00 0.09 0.21 0.42 0.67 0.85 0.93 1.00 1.00 1.00 +
2013 0.00 0.00 0.00 0.00 0.01 0.11 0.40 0.69 0.79 0.98 0.95 1.00 1.00 +
2014 0.00 0.00 0.00 0.00 0.03 0.10 0.41 0.76 0.87 0.97 0.98 0.96 1.00 +
2015 0.00 0.00 0.00 0.00 0.00 0.06 0.16 0.65 0.91 0.97 0.95 1.00 1.00 +
2016 0.00 0.00 0.00 0.00 0.00 0.04 0.16 0.54 0.78 0.95 0.95 1.00 1.00 1.00
2017 0.00 0.00 0.00 0.02 0.00 0.09 0.34 0.65 0.89 1.00 1.00 0.97 1.00 1.00
2018 0.00 0.00 0.00 0.00 0.02 0.13 0.32 0.56 0.84 0.96 1.00 0.97 0.97 1.00
2019 0.00 0.00 0.00 0.00 0.01 0.12 0.34 0.76 0.89 0.86 0.95 1.00 1.00 1.00
2020 0.00 0.00 0.00 0.00 0.01 0.11 0.29 0.63 0.82 0.89 1.00 1.00 1.00 1.00
2021 0.00 0.01* 0.00 0.00 0.00 0.14 0.33 0.58 0.84 0.95 0.96 1.00 1.00 +
2022 0.00 0.00 0.02 0.00 0.00 0.06 0.39 0.63 0.66 0.96 1.00 0.96 1.00 -
Table 5.13. COD. Proportion mature at age from bottom trawl surveys in the Barents Sea standard area winter 1994-2022. Bootstrap mean estimate. The proportion mature is the number of fish classified as maturity category 2 and 3, divided by the total number of fish assigned categories 1-3.

* Based on one sample only.

5.5 - Stomach sampling

Since 1984, cod stomachs have been sampled regularly during the winter survey. The sampling strategy has generally been the same as that for sampling otoliths. Stomach have been frozen on board and analysed in the laboratory, except for the period 1994-2000, when some of the stomachs were analysed on board and only the main prey categories were identified. For details about the sampling methodology and the Norwegian-Russian cooperation on diet investigations in the Barents Sea, see Mehl and Yaragina (1992) and Dolgov et al . (2007).

The number of stations and stomachs sampled as well as the proportion of empty stomachs and the mean stomach fullness index (SFI, see below) for each of four size groups (≤ 19 cm, 20-34 cm, 35-49 cm, ≥ 50 cm) is given in Table 5.14. Tables 5.15 - 5.18 show the mean diet composition by prey species/groups by year for each size group. Note that in the years 1994-2000, blue whiting, long rough dab and Norway pout were included in the category ‘other fish’ when stomachs were analysed on board.

The stomach fullness index is calculated as SFIi=100*ΣWSi/Wi, where WSi is the weight (g) of the stomach of fish i, and Wi is the weight (g) of fish i . For 1987 SFI has not been calculated, because very few fish were weighed that year due to technical problems. The distribution on prey groups has been adjusted by distributing the unidentified component of the diet proportionally among the various components, taking into account the level of identification.

The proportion of empty stomachs is largest for the smallest fish (Table 5.14), a pattern seen for all years. The stomach fullness in 2021 was lower than in 2020 for all length groups except cod ≤ 19 cm. Capelin is the dominating prey for cod ≥ 20 cm, followed by shrimp (Tables 5.16-5.18), while krill dominates for the smallest cod (Table 5.15). However, in many years capelin is also an important prey for the smallest cod. The proportion of capelin in the diet decreased from 2020 to 2021 for cod ≥ 30 cm while it increased for smaller cod. Cod cannibalism as proportion of the diet has shown a decreasing trend in recent years.

    no. stomachs sampled % empty stomachs mean stomach fullness
Year Stations <20 cm 20-34 cm 35-49 cm >=50 cm <20 cm 20-34 cm 35-49 cm >=50 cm <20 cm 20-34 cm 35-49 cm >=50 cm
1984 31 176 288 242 381 18.8 14.9 5.0 4.5 1.59 2.05 1.80 1.46
1985 49 106 494 582 612 44.3 34.0 19.8 20.6 1.55 3.58 4.46 3.43
1986 73 231 309 398 427 43.3 32.4 26.9 19.0 0.73 2.48 2.90 2.94
1987 52 133 415 501 409 32.3 48.9 45.3 48.9        
1988 79 29 418 844 704 34.5 40.2 31.6 29.7 1.01 1.29 0.91 0.84
1989 82 82 378 890 1132 40.2 21.2 16.3 20.6 1.45 2.28 2.12 1.47
1990 60 177 300 450 870 39.0 22.7 18.4 16.4 1.84 2.18 2.01 1.60
1991 70 271 463 450 1107 40.6 25.5 11.3 9.5 0.95 2.28 3.73 4.27
1992 100 229 382 471 922 65.9 45.8 31.4 38.2 1.79 3.15 3.05 1.92
1993 117 139 393 570 1073 76.3 38.4 21.2 26.7 1.86 3.34 2.99 3.05
1994 138 296 370 580 1163 64.9 34.9 25.0 24.3 0.76 2.04 2.00 1.63
1995 161 452 517 638 1482 52.2 36.4 32.0 30.8 1.16 1.39 0.93 0.80
1996 254 483 507 540 1338 55.7 39.1 28.0 27.4 0.92 1.32 1.38 1.02
1997 149 305 337 358 1105 57.0 34.1 20.7 29.5 0.98 1.60 1.81 1.48
1998 197 496 492 564 1042 64.7 48.2 29.3 28.6 2.20 1.93 1.67 1.22
1999 211 310 471 554 849 61.3 38.6 27.4 25.9 2.11 1.90 2.06 1.76
2000 243 413 645 669 1069 53.8 28.7 21.2 21.1 1.36 1.98 2.41 1.74
2001 361 644 728 884 1485 72.4 42.3 29.3 32.2 2.32 2.98 3.33 2.79
2002 345 393 704 799 1423 69.2 42.8 30.9 30.9 1.57 2.78 2.36 1.88
2003 285 325 499 637 1468 61.5 39.5 22.6 24.4 5.55 2.78 2.55 2.28
2004 329 508 525 663 1522 51.8 37.9 24.1 27.6 1.94 2.02 1.76 1.55
2005 335 509 651 648 1423 43.6 34.7 26.5 25.4 2.29 2.22 1.79 1.65
2006 259 402 464 534 1059 59.2 42.5 21.9 24.5 1.80 1.88 2.56 1.80
2007 273 386 483 592 1341 60.6 45.3 30.7 30.1 1.68 1.87 1.83 1.50
2008 326 260 733 933 1655 61.9 38.5 26.0 23.0 1.94 2.42 2.93 2.19
2009 319 385 547 798 1657 56.1 35.1 22.3 23.9 1.57 1.89 2.02 1.58
2010 360 594 552 748 2079 51.5 38.6 23.0 25.5 1.83 2.19 2.72 2.49
2011 359 515 628 506 1821 56.7 37.7 17.2 23.9 2.08 2.06 2.47 2.49
2012 297 373 408 431 1626 42.6 27.5 13.9 21.0 1.80 2.45 2.28 1.67
2013 279 209 352 425 1435 44.0 28.4 12.7 17.2 1.49 2.25 2.36 1.93
2014 434 570 686 686 2004 42.8 26.7 18.4 19.8 1.59 2.17 2.11 1.33
2015 356 664 562 670 1735 45.8 29.9 20.1 23.1 1.53 2.09 1.96 1.59
2016 387 427 616 728 1971 52.5 32.0 25.4 24.2 1.51 1.92 2.03 1.56
2017 293 339 465 529 1416 46.0 35.5 28.5 28.2 1.90 1.99 1.66 1.50
2018 432 638 850 935 2086 44.8 28.1 19.4 17.5 1.50 2.07 2.29 1.74
2019 506 787 974 1095 2302 46.1 29.6 19.1 17.2 1.60 1.95 2.04 1.87
2020 458 633 952 992 2369 38.1 28.2 18.2 18.0 1.71 1.98 2.33 2.16
2021 447 385 824 899 1842 49.1 23.1 12.7 16.5 2.53 1.71 1.80 2.05
Table 5.14. Number of stations and stomachs sampled, % empty stomachs, and mean stomach fullness by length group in the Barents Sea winter 1984-2021.
Year Amphipods Krill Shrimp Other invertebrates Capelin Herring Polar cod Blue Cod Haddock Redfish Long rough dab Norway Other
whiting pout fish
1984 1.2 7.7 37.5 4.5 13.3           35.8      
1985 15.5 7.9 27.9 44.4                   4.3
1986 14.3 3.8 34.0 14.4 15.2                 18.3
1987 24.8 17.7 10.9 0.2 25.4   21.0              
1988 3.5 19.2   64.3             13.0      
1989 41.1 27.9   31.0                    
1990 5.5 14.2 38.4 3.7 3.8           3.2     31.2
1991 12.2 18.7 6.9 8.4 53.8                  
1992 3.7 3.8 6.9 54.3 17.7                 13.6
1993 35.3 59.0   5.7                    
1994 19.1 40.8 10.9 11.6                   17.6
1995 12.9 6.7 33.9 3.5 7.4   27.8   6.2         1.6
1996 16.3 25.4 15.0 27.4 9.4                 6.5
1997 23.3 35.9 26.5 0.3                   14.0
1998 20.9 30.3 17.2 12.4 16.9             2.3    
1999 9.9 18.4 34.0 6.5   18.0 13.2              
2000 3.3 57.1 17.8 0.0 17.3                 4.5
2001 7.0 31.2 10.1 10.7 26.8 8.6               5.6
2002 15.0 32.1 21.1 13.9 17.9                  
2003 1.6 80.0 10.4 1.4 6.6                  
2004 11.0 44.7 5.9 9.1 14.3 4.2 10.8              
2005 17.2 22.8 16.2 0.3 35.8                 7.7
2006 9.7 49.9 7.8 20.5 12.1                  
2007 6.0 74.6 6.1 0.5 11.6             1.2    
2008 7.3 47.6 31.3 8.7 0.7             0.3   4.1
2009 4.7 61.4 1.9 8.8 18.1                 5.1
2010 3.5 41.7 1.4 1.6 48.2           0.7     2.9
2011 1.5 24.8 14.6 4.0 29.6           8.2     17.3
2012 4.7 20.2 8.5 4.0 53.0                 9.6
2013 2.2 66.2   17.8                   13.8
2014 8.9 42.6 12.7 8.9 26.8                 0.1
2015 2.8 44.8 10.6 13.6 22.1                 6.1
2016 15.7 39.7 9.6 5.6 21.5                 7.9
2017 12.7 6.9 1.0 38.0 0.9           31.0     9.5
2018 9.0 43.9 11.2 9.6 19.0                 7.3
2019 7.5 34.9 13.9 9.8 27.7               2.2 4.0
2020 10.4 53.9 4.4 9.1 13.2       2.2     1.4   5.4
2021 6.0 45.2 8.4 2.5 31.7             2.1 4.1  
Table 5.15. Mean stomach content composition (% of total SFI) of cod ≤ 19 cm from the survey in the Barents Sea winter 1984-2021.
Year Amphipods Krill Shrimp Other invertebrates Capelin Herring Polar cod Blue Cod Haddock Redfish Long rough dab Norway Other
whiting pout fish
1984 0.1 0.1 21.0 2.7 40.2   8.1       26.3 0.2   1.3
1985 0.2 0.1 17.0 2.0 69.2 9.3       1.1 0.2     0.9
1986 2.0 1.1 5.9 2.8 56.2 7.0       0.8 23.3     0.9
1987 0.5 1.9 25.2 0.3 53.7       6.6   11.4     0.4
1988 0.9 0.2 20.7 7.0 52.9           18.3      
1989 11.9 7.1 9.0 5.6 33.2   5.4   1.6   25.4 0.5   0.3
1990 0.6 0.5 18.5 0.7 66.7           8.4     4.6
1991 0.1 0.2 4.3 0.2 92.5           2.0     0.7
1992 0.4 0.8 6.4 1.2 88.1       0.4   2.5     0.2
1993 0.1 0.6 8.1 0.3 78.4 5.9 3.8   0.9 1.1 0.1     0.7
1994 1.2 10.2 8.3 1.7 54.9 14.2 4.8   1.7   1.2     1.8
1995 1.4 1.5 9.4 1.8 45.8   10.8 0.6 13.3 3.4 9.3     2.7
1996 1.9 0.5 13.6 1.3 48.9   5.3   24.9   1.8 0.3 0.8 0.7
1997 1.1 3.4 17.6 1.6 42.6   1.2 5.4 10.0         17.1
1998 2.2 2.6 23.5 1.6 47.8 3.4     10.3     5.6   3.0
1999 2.3 4.0 24.5 3.4 45.6 13.5 0.8   3.2 2.7        
2000 0.7 8.0 14.2 0.3 59.4 4.2 5.3   3.6 2.1   0.1   2.1
2001 0.9 2.8 8.5 2.8 69.4 4.7 5.6   4.0         1.3
2002 0.5 1.6 12.2 2.9 71.2 0.7 7.0     1.9       2.0
2003 0.5 2.4 7.3 0.7 71.9 14.4     2.1     0.1 0.5 0.1
2004 2.1 5.2 9.7 1.9 60.6 5.9 6.4   1.9 4.2       2.1
2005 0.6 2.3 12.0 0.9 61.2 3.6 7.7   5.7       4.9 1.1
2006 1.4 1.5 11.8 3.2 66.6 1.6 2.8 2.1   3.4     4.9 0.7
2007 2.3 4.8 15.0 7.3 58.8 0.1       7.7 3.7     0.3
2008 0.5 3.8 11.1 4.7 63.3   3.5     2.4 4.2 1.0   5.5
2009 0.5 6.6 8.8 5.6 71.2   2.4   1.5   0.2     3.2
2010 0.7 5.2 7.4 1.8 74.2 1.0     6.4   2.2     1.1
2011 0.9 3.3 8.3 3.7 74.3       1.1   6.0 0.1 1.1 1.2
2012 0.4 2.6 7.2 2.3 77.1 0.4     7.7         2.3
2013 0.3 7.2 10.4 3.4 68.0   2.1   4.3   0.3 0.1   3.9
2014 2.6 3.5 6.3 5.8 74.7 1.7     1.5 0.1       3.8
2015 0.9 2.4 9.8 3.4 75.9       3.7 1.6   0.3   2.0
2016 2.7 5.8 9.1 6.0 65.2         3.7 0.7     6.8
2017 0.4 3.3 7.8 4.6 67.0 1.7       4.5 2.0 6.7   2.0
2018 1.2 6.5 4.9 6.5 64.6 3.0     7.8 1.7 0.1   2.0 1.7
2019 0.6 4.4 9.2 9.1 64.7 0.5     7.6 1.4       2.5
2020 2.8 12.4 7.4 7.0 64.5       1.4 0.5 0.7 0.4   2.9
2021 2.2 14.1 16.2 10.3 42.1   2.6       4.3 0.9   7.3
Table 5.16. Mean stomach content composition (% of total SFI) of cod 20-34 cm from the survey in the Barents Sea winter 1984-2022.
Year Amphipods Krill Shrimp Other invertebrates Capelin Herring Polar cod Blue Cod Haddock Redfish Long rough dab Norway Other
whiting pout fish
1984 0.5   18.2 1.3 41.5       0.7 2.6 34.5 0.1 0.6  
1985 0.5   4.7 0.2 88.7 4.2     0.5 0.2 0.9     0.1
1986 0.8 2.5 6.8 3.6 58.4 12.4         15.3     0.2
1987 0.5 0.2 22.9 1.7 47.9 9.2 1.8   4.4 2.0 5.5   3.8 0.1
1988 1.0 1.9 29.1 6.3 51.2     1.5     8.8     0.2
1989 4.1 1.8 11.3 3.3 50.2   7.9   0.2   18.6 0.8 0.2 1.6
1990 0.1 0.1 7.4 1.6 84.8 2.0       1.3 2.5   0.2  
1991 0.1 0.1 1.8 0.6 94.0         1.5 1.2 0.1   0.6
1992   0.1 3.3 3.7 79.7 9.1     0.3 0.3 1.2   1.7 0.6
1993 0.1 0.2 6.0 0.6 85.4 5.6 0.5   0.2 0.4   0.2 0.8  
1994 0.9 14.2 6.9 1.2 48.9 13.5 9.1   2.2 0.4 0.3     2.4
1995 0.9 0.6 12.8 2.2 44.7 6.2 1.2   17.9 8.6 4.7     0.2
1996 1.8 0.7 10.0 2.2 21.6 1.5 2.1 5.5 37.4 6.7 2.5   6.9 1.1
1997 0.9 0.3 14.8 4.3 40.3   5.2 3.6 17.1 3.7 0.5 0.1 1.2 8.0
1998 1.1 0.4 23.2 6.8 50.3 8.5 1.2 1.8 4.1 1.5 0.8     0.3
1999 0.3 0.4 28.0 1.8 44.9 12.0 2.4   1.9 5.7 0.5 0.1 0.4 1.6
2000 0.9 0.3 8.2 0.6 83.5 4.1 0.4   0.7 0.3       1.0
2001 0.4 0.2 6.3 3.3 73.6 5.2 7.3 1.4 1.1 0.5   0.3   0.4
2002 0.2 0.6 10.4 4.2 68.3 2.3 4.8 0.8 3.2 3.9   0.5 0.4 0.4
2003 0.3 1.1 8.2 1.6 68.4 11.1 1.2 0.2 2.7 4.9       0.3
2004 0.9 1.6 14.5 4.5 61.7 6.5 2.3 1.0 4.1 1.5     1.0 0.4
2005 0.7 0.7 13.7 2.1 58.3 3.1 3.6 1.9 0.2 13.2   0.3 1.4 0.8
2006 0.1 0.2 13.1 1.5 64.8 2.0 1.3 1.6 1.1 12.7   0.2 0.3 1.1
2007 3.5 0.8 18.7 2.4 47.6 7.8   0.2 1.1 13.1 0.4 0.4 3.3 0.7
2008 0.3 0.9 11.7 1.3 71.9 2.7 7.4     0.9 1.1 0.3 0.4 1.1
2009 0.8 1.7 6.9 6.9 75.9 1.8 2.4   1.7 0.4 0.6 0.1 0.8  
2010 1.0 1.2 6.3 1.3 81.2 0.4 0.3   2.2 3.6 1.4 0.1 0.6 0.4
2011 0.1 0.7 7.5 3.2 76.0 1.5   1.4 4.2 0.9 2.3 0.1 1.4 0.7
2012 0.5 0.9 7.7 4.3 71.2 0.5 0.8 0.3 4.2 4.4 0.8 0.3 2.6 1.5
2013 0.4 1.5 7.9 4.6 77.9   1.1   3.3 1.6 0.3 0.1 0.3 1.0
2014 0.3 0.6 10.5 3.9 74.4 1.8     1.6 4.3 0.6 0.1 0.9 1.0
2015 0.5 3.2 7.9 2.3 77.1 1.3 0.2 2.3 2.4 1.1 0.3 0.4   1.0
2016 3.3 1.0 8.8 5.7 68.2 1.3     2.2 5.7 1.1 0.7 0.7 1.3
2017 0.1 1.1 12.3 4.1 70.5       0.4 5.6 0.7   2.6 2.6
2018 0.2 2.0 6.5 2.4 70.0 5.9     7.0 5.0 0.3   0.2 0.5
2019 0.5 1.1 9.8 3.0 69.8 3.9     6.1 4.0 0.4 0.1   1.3
2020 1.6 2.5 7.5 3.1 81.1 2.0     1.5 0.1 0.2 0.2   0.2
2021 2.6 3.5 20.0 5.7 55.9 1.4 2.6 0.4 0.6 0.6 4.7 0.5   1.5
Table 5.17. Mean stomach content composition (% of total SFI) of cod 35-49 cm from the survey in the Barents Sea winter 1984-2021.
Year Amphipods Krill Shrimp Other invertebrates Capelin Herring Polar cod Blue Cod Haddock Redfish Long rough dab Norway Other
whiting pout fish
1984 0.4   16.3 1.3 48.1   0.6   3.5 2.4 26.4 0.3   0.7
1985 0.2   5.2 0.4 85.8 3.0   0.3 2.1 0.6 1.2 1.1 0.1  
1986 0.6 0.2 4.4 3.9 53.9 3.2   2.5 9.5 7.9 7.7 0.1 4.1 2.0
1987 1.9 0.1 7.4 6.5 2.2 3.6 3.1 3.3 15.6   35.3 0.3 18.9 1.8
1988 0.9 0.7 11.7 7.0 11.9     4.8 0.0   16.3 4.7   42.0
1989 0.8 1.0 10.1 7.2 50.9   1.1   0.0 0.5 25.1 1.2 0.8 1.3
1990 0.1 0.3 5.2 1.8 74.4 1.1   5.2 0.1 4.8 4.0 0.9 1.8 0.3
1991     1.2 0.5 94.1 0.4     0.6 0.9 1.0 0.1 0.4 0.8
1992 0.2 0.1 5.6 3.8 56.7 17.6 0.1   2.3 4.1 3.7 2.3 2.6 0.9
1993   0.3 2.2 11.4 54.9 16.0 0.3 0.6 5.2 4.3 0.9 0.0 3.8 0.1
1994 0.5 12.9 5.9 2.8 35.4 7.1 4.4 0.2 12.0 4.3 5.8 1.1   7.6
1995 0.5 0.3 5.0 2.2 8.4 8.0 0.7   18.3 20.4 18.8 2.2 0.2 15.0
1996 0.5 0.2 4.1 2.7 9.3 14.6 2.5 0.4 27.2 27.8 6.2 1.8 2.6 0.1
1997 0.2 0.2 10.1 0.8 45.8 5.0 1.1 3.4 5.3 8.2 4.3 0.8 0.6 14.2
1998 1.2 0.2 22.7 3.8 34.5 7.3 1.0 1.2 6.2 6.6 4.1 3.7 2.6 4.9
1999 0.2 0.1 25.8 6.3 26.5 9.8 2.5 0.7 10.3 5.0 0.4 1.4 0.5 10.5
2000 0.9 0.4 7.9 1.6 68.9 6.5 0.8 2.3 2.8 3.4 0.7 1.5   2.3
2001 0.7 0.2 4.4 4.6 71.7 4.4 1.6 2.5 3.3 2.6 0.3 1.9 0.4 1.4
2002 0.2 0.7 5.9 6.5 50.9 3.0 4.2 2.0 9.0 13.0 1.0 1.7 0.7 1.2
2003 0.1 0.2 5.5 4.9 59.1 10.6 1.5 1.1 4.3 9.1 0.5 1.4 0.4 1.3
2004 0.2 0.2 6.5 3.2 48.2 4.9 0.5 2.6 7.6 17.0 1.6 2.7 1.6 3.2
2005 0.3 0.3 5.8 4.2 33.2 2.9 0.8 5.6 7.9 31.2   1.5 2.5 3.8
2006 0.1 0.1 4.6 4.8 45.8 1.8 0.6 6.1 1.8 28.3 1.6 1.8 1.5 1.1
2007 0.5 0.2 8.3 5.0 29.2 18.4   1.9 7.8 20.8 2.0 2.3 2.7 0.9
2008 0.1 0.4 4.9 2.7 60.7 7.5 0.3 0.4 0.9 17.4 0.8 1.8 0.9 1.2
2009 0.2 0.3 5.5 4.2 53.0 8.6 0.8 0.4 4.1 12.9 1.5 2.9 3.9 1.7
2010 0.6 0.3 2.5 2.3 72.7 1.7 0.2 0.1 3.5 10.6 0.9 2.0 2.5 0.1
2011 0.1 0.3 3.1 2.9 82.0 0.4 0.6   2.6 5.2 0.9 0.5 1.1 0.3
2012 0.1 0.2 4.0 7.1 60.9   0.1 0.1 2.6 16.7 0.5 1.1 3.8 2.8
2013 0.3 0.7 4.1 7.6 67.9 0.2 0.4 0.6 5.1 8.3 0.9 1.4 1.8 0.7
2014 0.5 0.5 5.6 10.4 55.4 2.2   0.2 6.3 10.9 1.0 3.1 1.6 2.3
2015 0.2 0.1 4.1 6.7 69.9 1.1   1.1 2.9 6.8 2.1 1.3 2.4 1.3
2016 1.0 0.9 3.4 14.8 60.0 2.9 0.1 0.7 5.3 6.5 0.7 2.7 0.4 0.6
2017 0.1 0.6 2.9 4.2 74.2 1.4   1.5 0.6 10.7 1.3 1.2 1.0 0.3
2018 0.1 0.9 3.7 9.5 51.7 2.5 0.1 0.1 8.1 19.3 0.7 2.0 0.7 0.6
2019 0.4 0.5 3.8 6.6 68.4 2.8 0.1 0.2 5.5 7.4 1.0 0.5 1.9 0.9
2020 0.4 0.8 2.6 7.5 59.3 5.5 0.0 0.2 13.4 4.8 1.8 1.9 1.0 0.8
2021 0.4 1.1 5.2 9.3 51.0 10.6 3.9 0.1 3.6 8.1 2.3 2.8   1.6
Table 5.18. Mean stomach content composition (% of total SFI) of cod ≥ 50 cm from the survey in the Barents Sea winter 1984-2021.

6 - Distribution and abundance of haddock

6.1 - Acoustic estimation

As for cod, it is expected that the survey best covers the immature part of the haddock stock. At this time of the year a large proportion of the mature haddock (age 6 and older) is on its spawning migration south-westwards out of the investigated area. In some earlier years, e.g., 2004 and 2005, concentrations of mature haddock have been observed pelagically rather far above bottom along the shelf edge. The bottom trawl sampling poorly covers these concentrations. There are indications that the distribution of age groups 1 and 2 in some years are concentrated in coastal areas not well covered by the survey. This occurred in the late 1990s and will have strongest effect on poor year-classes. In the later surveys, small haddock have been widely distributed, and the strong year-classes have been found unusually far to the north. Favourably hydrographic conditions and/or density dependent mechanisms might cause this. However, it is difficult to separate the two factors.

Figure 6.1 shows the spatial distribution of acoustic registrations assigned to haddock in 2022. The registrations reflect the general distribution of haddock in the southern and eastern Barents Sea. The overall echo abundance in 2022 was higher than the very low registrations in 2021, with several coastal transects registering NASC-values above 500 (up to 700 m2/nmi2 ).

 

HADDOCK NASC. Distribution of acoustic backscatter (m2/nmi2) assigned to haddock in 2022. The black lines without yellow circles represent parts of the cruise track where the acoustic backscatter was scrutinized but not assigned to haddock. NASC values < 5 was set to zero for this illustration. Circles with red outline represent NASC > 500.
Figure 6.1. HADDOCK NASC. Distribution of acoustic backscatter (m2/nmi2 ) assigned to haddock in 2022. The black lines without yellow circles represent parts of the cruise track where the acoustic backscatter was scrutinized but not assigned to haddock. NASC values < 5 was set to zero for this illustration. Circles with red outline represent NASC > 500.

 

Table 6.1 shows the acoustic abundance indices by age within the main areas. As in most of the previous years the highest abundance was observed in main area D. The full time series is presented in Table 6.2. Abundance of age 1 in 2022 increased compared to 2020 and 2021 when it was very low. This is reflected in low abundances of ages 2 and 3 in 2022. Abundance of age 6 in 2022 was quite high, while abundance of older fish (age 8+) kept declining from the high in 2013-2014.

The strong 2004-2006 year-classes can be followed through the time series. In later years, the 2009, 2011, and 2013-2018 year-classes seem to be fairly strong. In particular the year-classes 2016 and 2017 have high indices at age 1-2. The year-class 2019 appears to be much weaker as the abundance of 1-year-olds observed in 2020 is the third lowest in the time series. The estimate of this year-class as 2-year-olds in 2021 are only half of the previously lowest estimate in the time series. Abundance of the 2020 year-class, while still on the low side, is nearly 60 % higher than the 2019 year-class, while the 2021 year-class is much stronger and above average in the time series.

The abundance of old fish (particularly age 14) was higher in 2020 than previously observed. This likely reflects the surviving individuals from the 2005-2006 year-classes. However, few of these fish appear to have survived and become part of the 15+ group in 2021 and 2022.

Table 6.3 shows indices for strata 24-26, which are also included in the full time series (Table 6.2). The contribution from main area N was rather low in all years, except in 2018 when 29% of age 1 haddock (by number) was found in the extended area, contributing 13 % of the total stock biomass index. The total abundance in area N in 2022 is comparable to the abundance in 2019 and much higher than in 2020-2021.

Table 6.4 presents estimated coefficients of variation (CV) for haddock age groups 1-14. In most years, CVs for age groups older than 7 years are above what could be considered as acceptable (approximately 20 %). In recent years, younger ages have also had relatively high CVs, which may indicate patchier distributions in a situation with low abundance.

Age group Total Biomass (‘000 t)
Area 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
A 250.1 10.2 0.87 3.46 8.20 9.06 2.92 0.05 0.02 0.18 0.63 0.00 0.00 0.00 0.00 285.7 33.3
B 170.0 11.9 4.30 2.07 10.0 6.29 0.98 0.09 0.05 0.00 0.00 0.00 0.00 0.00 0.00 205.8 128.5
C 398.6 15.4 2.25 11.1 12.4 21.1 2.95 0.18 0.00 0.00 0.00 0.00 0.00 0.05 0.00 464.0 11.4
D 609.6 27.1 3.60 41.8 50.1 52.2 3.15 0.24 0.07 0.03 0.00 0.00 0.00 0.01 0.00 787.8 1.31
D'1 35.3 0.34 0.24 3.60 5.44 5.09 0.17 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00 50.2 18.3
E 73.4 0.18 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 73.6 10.3
S 157.7 1.20 0.04 0.73 5.40 5.87 1.30 0.19 0.00 0.00 0.04 0.00 0.00 0.00 0.00 172.4 27.7
N 102.5 3.81 0.05 0.61 3.72 1.70 0.31 0.05 0.00 0.00 0.00 0.00 0.00 0.00 0.00 112.7 51.8
ABCD 1428.3 64.6 11.0 58.5 80.7 88.6 10.0 0.6 0.1 0.2 0.6 0.00 0.00 0.1 0.00 1743.3 174.5
AN 1797.1 70.2 11.4 63.4 95.3 101.2 11.8 0.8 0.1 0.2 0.7 0.00 0.00 0.1 0.00 2152.2 282.6
Table 6.1. HADDOCK. Abundance indices (numbers in millions) for the main areas of the Barents Sea from acoustic survey winter 2022 estimated by StoX software.
Age group Total Biomass (‘000 t)
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
1994 887.82 187.96 348.73 626.65 121.38 8.55 0.70 0.33 0.61 0.48 1.46 0.16 0.00 0.00 0.00 2184.83 643.51
1995 1198.18 88.59 41.47 121.49 395.37 47.61 2.80 0.05 0.12 0.03 0.00 0.54 0.14 0.00 0.00 1896.39 508.78
1996 132.60 94.52 29.97 22.09 68.65 143.69 5.67 0.93 0.00 0.01 0.00 0.02 0.04 0.00 0.00 498.19 248.35
19971 508.87 26.51 57.27 22.22 15.47 56.13 62.77 4.68 0.07 0.00 0.00 0.01 0.05 0.06 0.00 754.11 201.67
19981 210.96 150.99 33.78 58.79 24.20 7.70 14.06 20.69 1.44 0.02 0.04 0.00 0.00 0.00 0.12 522.78 150.98
1999 653.40 30.11 83.67 21.64 22.10 6.17 1.55 3.88 2.72 0.03 0.00 0.02 0.00 0.00 0.00 825.29 107.86
2000 1063.01 404.77 36.39 75.53 14.01 12.61 1.57 0.53 2.01 0.69 0.17 0.13 0.02 0.00 0.00 1611.44 189.81
2001 753.01 266.12 233.45 40.20 41.38 2.20 1.61 0.15 0.09 0.14 0.28 0.09 0.09 0.00 0.02 1338.83 206.40
2002 1315.15 267.90 255.20 201.84 18.47 11.70 1.59 0.29 0.03 0.13 0.26 0.09 0.05 0.00 0.00 2072.70 298.25
2003 2743.74 362.35 203.68 184.57 136.04 12.26 6.01 0.26 0.14 0.26 0.34 0.09 0.07 0.00 0.00 3649.81 444.48
2004 528.97 466.54 151.01 101.85 107.82 57.68 7.61 1.15 0.29 0.04 0.05 0.05 0.04 0.08 0.00 1423.18 322.95
2005 2276.46 143.98 221.33 115.67 57.43 56.71 12.69 0.38 0.32 0.01 0.00 0.00 0.00 0.00 0.00 2884.98 305.99
20062 2091.11 624.78 56.32 123.84 47.37 19.26 13.64 3.23 0.08 0.15 0.00 0.03 0.00 0.00 0.09 2979.90 297.84
20071 2015.71 953.50 209.28 46.14 80.57 28.92 10.00 5.05 2.26 0.30 0.18 0.00 0.00 0.00 0.05 3351.97 401.72
2008 778.39 1753.54 812.41 303.04 90.02 74.12 7.41 12.77 1.63 0.14 0.16 0.18 0.00 0.00 0.00 3833.81 920.38
2009 443.93 209.05 883.68 629.98 266.65 38.87 14.57 1.26 0.34 0.66 0.00 0.05 0.00 0.00 0.00 2489.04 865.44
2010 1559.42 86.03 128.07 631.03 603.99 166.96 12.07 2.94 0.96 0.99 0.10 0.06 0.00 0.00 0.00 3192.62 1035.93
2011 428.46 288.27 54.16 84.23 313.02 292.21 54.91 1.71 0.96 0.23 0.00 0.20 0.07 0.00 0.00 1518.43 712.08
20123 1583.44 94.54 191.63 48.84 88.12 310.60 172.52 30.09 0.52 0.34 0.02 0.13 0.00 0.00 0.00 2520.79 814.60
2013 292.71 407.16 67.29 146.77 35.41 53.03 223.77 102.68 14.12 0.25 0.00 0.00 0.00 0.00 0.00 1343.19 759.62
2014 1838.71 109.92 334.82 39.12 108.72 23.18 34.77 86.36 36.63 1.66 0.52 0.00 0.00 0.01 0.00 2614.42 583.94
2015 1593.12 246.59 24.35 189.40 26.63 46.13 9.22 22.45 21.33 9.86 0.56 0.15 0.09 0.00 0.00 2189.88 387.71
2016 1276.00 107.18 71.81 12.08 59.62 12.52 17.28 7.48 17.21 12.74 2.76 0.48 0.00 0.03 0.02 1597.21 274.45
20173 3343.93 331.42 81.15 65.05 4.81 34.81 6.24 7.93 1.78 7.06 6.10 2.34 0.44 0.00 0.00 3893.06 338.87
2018 2925.90 810.16 171.03 62.74 64.40 6.77 15.57 2.75 2.57 1.56 5.56 2.99 1.87 0.14 0.00 4074.01 410.39
2019 1544.96 687.80 507.61 146.22 31.73 21.88 4.72 3.46 1.37 1.57 0.38 0.39 0.33 0.06 0.09 2952.57 396.54
20203 272.94 260.72 286.32 306.38 79.18 22.38 11.59 1.84 1.36 0.83 0.85 1.22 0.99 0.96 0.12 1247.68 381.58
20213 431.68 15.69 50.76 130.37 181.80 19.35 5.44 0.94 0.81 0.48 0.07 0.21 0.07 0.05 0.08 837.80 258.47
2022 1797.1 70.2 11.4 63.4 95.3 101.2 11.8 0.82 0.14 0.20 0.7 0.00 0.00 0.07 0.00 2152.2 282.60
Table 6.2. HADDOCK. Abundance indices (numbers in millions) from acoustic surveys in the Barents Sea winter 1994-2022 estimated by StoX software.

1 Indices raised to also represent the Russian EEZ.

2 Not complete coverage in southeast due to restrictions, strata 7 area set to default and strata 13 as in 2005

3 Indices raised to also represent uncovered parts of the Russian EEZ.

Age group Total Biomass (‘000 t)
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
2014 135.0 0.88 10.3 0.92 0.81 0.80 0.96 1.84 1.31 0.20 0.02 0 0 0 0 153.0 17.9
2015 71.2 22.2 0.71 17.9 1.10 6.77 0.90 1.31 4.01 3.03 0.14 0 0.09 0 0 129.4 48.2
2016 15.7 1.77 3.32 0.26 3.67 0.70 0.71 0.62 1.75 0.83 0.33 0 0 0 0 29.7 16.1
2017 80.1 8.20 1.23 2.28 0.40 2.60 0.40 0.92 0.29 0.64 0.61 0.33 0 0 0 98.0 18.1
2018 855.7 46.4 11.7 2.57 3.48 1.15 2.97 0.45 0.33 0.25 0.54 0.39 0.38 0 0 926.4 54.6
2019 67.68 25.50 16.12 5.59 1.07 1.01 0.13 0.11 0.05 0.03 0.03 0.09 0.03 0.05 0.00 118.11 17.84
2020 1.54 1.18 12.6 12.4 3.09 2.40 0.55 0.49 0.16 0.09 0.04 0.08 0.08 0.05 0 34.8 22.7
2021 5.47 0.44 0.23 4.87 7.44 0.73 0.28 0.14 0.08 0.01 0.05 0.02 0.05 0.00 0.00 19.8 13.4
2022 102.5 3.81 0.05 0.61 3.72 1.70 0.31 0.05 0.00 0.00 0.00 0.00 0.00 0.00 0.00 112.7 51.8
Table 6.3. HADDOCK. Abundance indices (numbers in millions) for new strata 24-26 from acoustic surveys in the Barents Sea winter 2014-2022 estimated by StoX software. In 2020, the main index was revised to include these strata.
Age group
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1994 11 12 10 9 12 21 44 53 39 55 31 103 - -
1995 16 22 24 15 10 15 34 128 85 114 - 55 90 -
1996 20 27 31 23 16 15 22 44 - 120 - 98 108 -
19971 12 17 14 16 16 12 14 33 53 - - 121 63 74
19981 14 15 15 13 14 21 17 15 50 107 109 - - -
1999 19 24 21 28 22 23 32 34 26 118 - 123 - -
2000 9 9 21 12 18 17 28 45 30 39 72 102 104 -
2001 17 16 16 25 16 30 35 65 66 96 62 94 86 -
2002 8 10 12 10 16 16 29 51 111 69 60 53 71 -
2003 11 11 11 9 15 25 38 80 106 90 76 102 107 -
2004 37 23 23 30 33 17 21 26 45 65 65 86 64 66
2005 10 16 11 15 12 16 19 59 76 104 - - - -
20062 12 10 27 20 12 15 20 33 66 67 - 78 - -
20071 9 7 9 12 12 15 21 29 40 52 88 - - -
2008 13 10 10 10 21 24 29 62 94 263 84 137 - -
2009 14 13 9 11 14 19 19 43 79 48 - 107 - -
2010 15 17 10 10 9 13 27 34 49 49 108 92 - -
2011 15 13 16 12 11 10 15 40 58 94 - 84 115 -
20122 16 28 16 35 24 20 20 27 86 50 105 68 - -
2013 14 13 22 11 22 16 13 15 26 59 - - - -
2014 13 19 12 20 18 17 16 15 15 44 79 - - 109
2015 14 17 24 13 23 21 27 23 20 55 64 65 - -
2016 11 15 15 19 12 14 15 19 17 15 30 43 - 70
20172 6 9 15 13 22 16 22 23 34 29 24 36 67 -
2018 8 8 9 13 17 29 22 29 34 30 27 28 54 81
2019 9 8 8 8 13 14 29 26 48 35 64 35 72 115
20202 15 14 11 12 12 14 19 26 30 48 54 49 43 50
20212 15 25 19 34 45 21 37 48 78 94 61 121 57 87
2022 14 17 26 15 13 13 20 41 71 77 57 - - 86
Table 6.4. HADDOCK. Estimates of coefficients of variation (%) for acoustic abundance indices. Barents Sea standard area winter 1994-2022.

1Russian EEZ not covered 2Russian EEZ partly covered

6.2 - Swept area estimation

Figures 6.2 - 6.5 show the geographic distribution of bottom trawl catch rates (number of fish per NM 2 ) for haddock size groups < 20 cm, 20-34 cm, 35-49 cm and ≥ 50 cm. Like in previous years, the distribution extends further to the north and to the east than what was usual in the 1990s.

Table 6.5 presents the indices for each age group by main areas. The time series is shown in Table 6.6. The swept area estimates, too, are highest in the east in area D. The 2016-2018 year-classes currently dominate the bottom trawl indices. The weak 2019 year-class noted for the acoustic index is evident also in the swept area estimates, which is not surprising given that the same biological data used to calculate swept area indices are used to allocate acoustic backscatter to age groups. Overall, this survey tracks both strong and poor year-classes fairly well. Compared to cod a lower proportion of haddock is found in the extended survey area (Table 6.7). In 2022, the extended area contributed about 4 % of total abundance and about 2 % of total biomass.

 

HADDOCK < 20 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 6.2. HADDOCK < 20 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

 

HADDOCK 35-49 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 6.3. HADDOCK 20-34 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

 

HADDOCK 20-34 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 6.4. HADDOCK 35-49 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2 ). Black crosses indicate zero catches and the stippled line the ice edge

 

 

HADDOCK ≥ 50 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 6.5. HADDOCK ≥ 50 cm. Distribution in valid bottom trawl catches winter 2022 (number per nm2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

Table 6.8 presents estimated coefficients of variation (CV) for haddock age groups 1-14. In most years, CVs for age groups older than 7 years are above what could be considered as acceptable (approximately 20 %) .

Age group Total Biomass (‘000 t)
Area 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
A 312.8 31.0 0.56 4.26 5.54 6.72 2.50 0.05 0.02 0.11 0.24 0.00 0.00 0.00 0.00 363.9 28.9
B 148.3 9.80 3.39 0.78 5.15 3.04 0.39 0.07 0.01 0.00 0.00 0.00 0.00 0.00 0.00 171.0 17.2
C 129.2 7.27 0.80 3.38 3.19 5.39 0.93 0.06 0.00 0.00 0.00 0.00 0.00 0.02 0.00 150.2 15.1
D 801.2 57.6 4.41 64.1 85.9 87.6 4.67 0.30 0.08 0.04 0.00 0.00 0.00 0.02 0.00 1105.9 212.2
D'1 33.9 1.03 3.01 13.4 17.4 7.99 0.35 0.04 0.00 0.00 0.00 0.00 0.00 0.00 0.00 77.0 28.5
E1 52.1 0.11 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 52.2 1.04
S 105.4 0.63 0.03 0.32 1.54 2.20 0.18 0.08 0.00 0.00 0.00 0.00 0.00 0.00 0.00 110.3 6.93
N 79.3 2.86 0.04 0.32 3.00 0.59 0.09 0.03 0.00 0.00 0.00 0.00 0.00 0.00 0.00 86.2 6.81
ABCD 1391.5 105.7 9.15 72.5 99.8 102.8 8.48 0.47 0.11 0.16 0.24 0.00 0.00 0.04 0.00 1791.0 273.5
AN 1662.1 110.3 12.2 86.5 121.7 113.6 9.10 0.62 0.11 0.16 0.24 0.00 0.00 0.04 0.00 2116.7 316.7
Table 6.5. HADDOCK. Abundance indices from bottom trawl hauls for main areas of the Barents Sea winter 2022 (numbers in millions). Bootstrap mean estimates.
Age group Total Biomass (‘000 t)4
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+    
1994 604.20 224.79 314.53 436.25 46.18 3.54 0.16 0.13 0.20 0.15 0.47 0.03 0.00 0.00 0.00 0.00 403.7
1995 1429.04 199.52 54.86 167.10 343.38 29.62 1.44 0.03 0.04 0.02 0.00 0.29 0.09 0.00 0.00 0.00 443.9
1996 300.78 265.08 55.84 31.33 150.77 238.11 16.13 1.15 0.00 0.01 0.00 0.03 0.03 0.00 0.00 0.00 431.9
19971 1117.83 90.81 79.63 39.86 18.25 61.57 88.41 3.28 0.08 0.00 0.00 0.00 0.03 0.02 0.00 0.00 273.3
19981 248.27 196.70 21.68 36.75 11.84 1.29 9.20 7.21 0.65 0.02 0.02 0.00 0.00 0.00 0.03 0.03 91.7
1999 1207.98 83.20 56.92 15.87 9.42 2.83 0.81 1.28 0.77 0.02 0.00 0.02 0.00 0.00 0.00 0.00 86.7
2000 832.30 437.22 24.08 35.24 6.79 4.13 0.68 0.08 0.80 0.22 0.03 0.03 0.01 0.00 0.00 0.00 124.1
2001 1230.98 446.84 294.00 26.25 23.00 1.63 0.75 0.06 0.06 0.05 0.16 0.09 0.02 0.00 0.00 0.01 227.7
2002 1700.19 475.31 312.87 185.45 12.42 8.04 0.85 0.22 0.01 0.09 0.16 0.04 0.04 0.00 0.00 0.00 308.4
2003 3327.32 471.68 352.24 174.45 72.71 5.10 1.68 0.12 0.10 0.10 0.10 0.01 0.01 0.00 0.00 0.00 411.5
2004 700.86 706.61 173.13 100.52 77.02 51.28 7.41 0.91 0.13 0.04 0.05 0.04 0.04 0.07 0.00 0.00 307.6
2005 4473.16 386.39 317.89 141.06 50.66 61.19 10.08 0.25 0.08 0.01 0.00 0.00 0.00 0.00 0.00 0.00 431.0
20062 4944.60 1310.22 78.80 130.76 46.05 20.87 16.21 3.18 0.09 0.15 0.00 0.05 0.00 0.00 0.04 0.03 454.2
20071 3731.19 1684.83 443.27 81.78 84.67 26.28 5.41 2.20 1.38 0.80 0.07 0.00 0.00 0.00 0.03 0.00 594.8
2008 853.09 2042.01 1591.03 583.61 53.08 54.73 6.79 10.25 0.23 0.05 0.08 0.05 0.00 0.00 0.00 0.00 1100.5
2009 562.61 317.05 1230.43 751.01 368.33 25.41 12.44 0.85 0.09 0.35 0.00 0.01 0.00 0.00 0.00 0.00 976.7
2010 1634.82 79.89 102.45 510.45 443.76 139.32 7.99 1.02 0.39 0.47 0.05 0.05 0.00 0.00 0.00 0.00 759.4
2011 676.31 353.87 52.88 123.63 469.48 290.04 65.24 1.42 1.12 0.00 0.00 0.15 0.03 0.00 0.00 0.00 827.5
20123 1866.96 137.38 316.08 28.79 74.71 267.94 154.60 24.77 3.11 0.28 0.04 0.08 0.00 0.00 0.00 0.00 740.3
2013 344.58 490.28 57.44 143.98 22.02 33.62 191.14 69.38 6.11 0.08 0.00 0.00 0.00 0.00 0.00 0.00 600.9
2014 1281.40 123.95 381.17 32.73 104.40 23.26 50.04 97.54 38.69 1.82 0.59 0.00 0.00 0.02 0.00 0.00 656.0
2015 1133.97 342.02 30.61 187.04 43.60 39.44 14.67 18.73 30.74 9.70 0.33 0.14 0.02 0.00 0.00 0.00 404.4
2016 2299.37 561.96 163.38 34.34 115.60 22.41 41.95 12.44 32.40 27.64 4.34 0.98 0.00 0.14 0.05 0.02 569.4
20173 5065.43 770.04 134.94 105.48 7.55 55.34 9.69 15.60 2.53 10.33 8.74 4.06 0.73 0.00 0.00 0.00 566.0
2018 3823.29 1675.64 336.31 86.66 65.76 7.77 15.59 3.62 2.56 1.70 4.72 4.00 1.38 0.13 0.00 0.00 574.8
2019 1898.20 1125.27 1075.55 187.22 49.40 17.00 4.04 2.95 0.74 1.08 0.19 0.35 0.20 0.05 0.00 0.02 600.0
20203 110.62 267.79 424.22 586.99 99.12 22.08 6.06 2.61 1.04 0.67 0.23 0.71 0.70 0.49 0.02 0.00 537.8
20213 406.30 25.12 109.80 175.26 262.62 19.19 3.65 0.71 0.20 0.13 0.08 0.31 0.18 0.05 0.00 1003.6 342.0
2022 1662.1 110.3 12.2 86.5 121.7 113.6 9.10 0.62 0.11 0.16 0.24 0.00 0.00 0.04 0.00 2116.7 316.7
Table 6.6. HADDOCK. Abundance indices (numbers in millions) from bottom trawl surveys in the Barents Sea standard area winter 1994-2022. Bootstrap mean estimates.

1 Indices raised to also represent the Russian EEZ.

2 Not complete coverage in southeast due to restrictions, strata 7 area set to default and strata 13 as in 2005.

3 Indices raised to also represent uncovered parts of the Russian EEZ.

4 1994-2020: for years with raising, estimated based on relationship between unraised numbers-at-age and biomass-at-age from StoX baseline run. From 2021: estimated based on relationship between unraised numbers-at-age and biomass-at-age bootstrap mean estimates from StoX.

Age group Total Biomass (‘000 t)
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15+
2014 128.7 1.26 12.3 0.65 2.22 0.12 3.38 1.16 0.74 0.07 0.0 0.0 0.0 0.0 0 150.6 20.9
2015 49.0 17.4 0.33 13.2 0.46 4.30 0.88 0.56 3.51 2.16 0.0 0.0 0.0 0.0 0 91.8 34.5
2016 42.6 4.50 10.2 0.51 9.69 2.45 1.43 2.41 4.80 3.13 0.36 0.0 0.0 0.0 0 82.0 45.7
2017 199.6 15.7 3.76 5.83 2.18 7.56 0.80 2.07 1.06 1.82 2.39 0.72 0.0 0.0 0 243.5 51.6
2018 1141.9 65.3 17.9 3.20 5.03 2.27 3.66 0.90 0.54 0.35 0.72 0.48 0.56 0.0 0 1242.8 77.9
2019 115.3 45.6 30.1 7.74 3.03 1.13 0.15 0.14 0.0 0.07 0.0 0.06 0.0 0.0 0.02 203.4 29.9
2020 3.61 3.93 35.1 33.1 8.11 7.89 1.93 1.05 0.54 0.28 0.13 0.25 0.27 0.11 0 96.3 63.2
2021 12.6 1.08 0.40 7.74 13.4 1.29 0.61 0.14 0.09 0.02 0.06 0.09 0.11 0.00 0.00 37.6 22.8
2022 79.3 2.86 0.04 0.32 3.00 0.59 0.09 0.03 0.00 0.00 0.00 0.00 0.00 0.00 0.00 86.2 6.81
Table 6.7. HADDOCK. Abundance indices (numbers in millions) for new strata 24-26 from bottom trawl surveys in the Barents Sea winter 2014-2022. 2014-2020: baseline estimates, from 2021: bootstrap mean estimates.
Age group
Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1994 11 13 15 13 15 29 52 45 33 52 38 97 - -
1995 12 19 28 29 16 21 38 180 75 97 - 58 97 -
1996 14 13 12 25 30 24 61 64 - 98 - 95 96 -
19971 13 35 13 15 17 21 18 57 54 - - - 64 92
19981 15 13 13 14 16 25 18 16 34 107 106 - - -
1999 15 37 14 24 21 24 25 31 22 89 - 97 - -
2000 9 9 18 9 16 14 34 51 31 34 63 91 105 -
2001 12 17 12 20 11 36 33 47 59 51 47 86 62 -
2002 9 11 10 10 22 17 27 39 81 60 48 51 75 -
2003 16 24 28 13 11 19 31 59 60 71 56 92 93 -
2004 9 12 15 16 10 13 28 24 43 56 58 93 60 54
2005 9 17 12 22 14 22 14 70 48 93 - - - -
20062 14 14 18 12 13 16 21 30 44 70 - 63 - -
20071 10 8 9 19 12 17 24 26 44 50 61 - - -
2008 12 17 15 13 19 30 27 81 42 81 68 88 - -
2009 13 20 15 21 24 18 32 27 91 68 - 94 - -
2010 10 17 18 22 18 18 25 29 42 55 144 167 - -
2011 10 10 14 25 18 13 20 38 73 - - 81 84 -
20122 19 28 17 16 15 13 15 33 73 48 83 61 - -
2013 12 12 13 14 27 24 27 14 26 50 - - - -
2014 7 26 12 22 16 22 20 14 24 40 55 - - 99
2015 7 13 26 14 44 11 25 18 21 28 40 51 97 -
2016 22 25 13 42 11 15 20 15 15 19 27 51 - 62
20172 5 13 15 12 20 14 21 27 25 18 21 36 77 -
2018 7 16 13 12 10 17 15 23 18 18 18 20 32 52
2019 9 11 15 12 27 12 40 20 30 30 35 29 35 46
20202 16 9 11 14 14 19 22 29 27 40 39 29 24 37
20212 12 22 17 16 22 13 21 25 47 46 47 66 42 69
2022 10 12 27 17 23 18 19 25 52 66 49 - - 65
Table 6.8. HADDOCK. Estimates of coefficients of variation (%) for swept area abundance indices. Barents Sea standard area winter 1994-2022.

1 Russian EEZ not covered

2Russian EEZ partly covered

6.3 - Survey mortalities

Survey mortalities based on the acoustic indices (Table 6.9) have varied between years, and for most age groups there are no obvious trends. However, there are signs of co-variability within years. Survey mortalities based on the bottom trawl indices increased considerably from 2016 to 2017 to among the highest in the ten last years and has since then remained high for some age groups. Survey mortalities from 2019-2020 and 2020-2021 stand out as some of the highest in the time series for several age groups.

Year 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9
      Acoustic investigations      
1994-95 2.30 1.51 1.05 0.46 0.94 1.12 2.64 1.01
1995-96 2.54 1.08 0.63 0.57 1.01 2.13 1.09 -
1996-97 1.61 0.50 0.30 0.35 0.20 0.83 0.19 2.60
1997-98 1.21 -0.24 -0.03 -0.09 0.70 1.38 1.11 1.18
1998-99 1.95 0.59 0.45 0.98 1.37 1.60 1.29 2.03
1999-00 0.48 -0.19 0.10 0.43 0.56 1.37 1.07 0.66
2000-01 1.38 0.55 -0.10 0.60 1.85 2.06 2.28 1.77
2001-02 1.03 0.04 0.15 0.78 1.26 0.32 1.71 1.67
2002-03 1.29 0.27 0.32 0.39 0.41 0.67 1.81 0.73
2003-04 1.77 0.88 0.69 0.54 0.86 0.48 1.65 -0.11
2004-05 1.30 0.75 0.27 0.57 0.64 1.51 3.00 1.28
2005-06 1.29 0.94 0.58 0.89 1.09 1.43 1.37 1.56
2006-07 0.79 1.09 0.20 0.43 0.49 0.66 0.99 0.36
2007-08 0.14 0.16 -0.37 -0.67 0.08 1.36 -0.25 1.13
2008-09 1.31 0.69 0.25 0.13 0.84 1.62 1.77 3.63
2009-10 1.64 0.49 0.34 0.04 0.47 1.17 1.60 0.27
2010-11 1.69 0.46 0.42 0.70 0.73 1.11 1.95 1.12
2011-12 1.51 0.41 0.10 -0.05 0.01 0.53 0.60 1.20
2012-13 1.36 0.34 0.27 0.32 0.51 0.33 0.52 0.76
2013-14 0.98 0.20 0.54 0.30 0.42 0.42 0.95 1.03
2014-15 2.01 1.51 0.57 0.39 0.86 0.92 0.44 1.40
2015-16 2.70 1.23 0.70 1.16 0.76 0.98 0.21 0.26
2016-17 1.35 0.28 0.10 0.92 0.54 0.69 0.78 1.43
2017-18 1.42 0.67 0.25 0.01 -0.36 0.79 0.82 1.13
2018-19 1.45 0.46 0.15 0.68 1.08 0.34 1.57 0.70
2019-20 1.78 0.88 0.50 0.61 0.35 0.64 0.98 0.88
2020-21 2.86 1.64 0.79 0.52 1.41 1.41 2.51 0.82
2021-22 1.82 0.32 -0.22 0.31 0.59 0.49 1.89 1.90
    Bottom trawl investigations    
1994-95 1.11 1.41 0.63 0.24 0.44 0.90 1.87 1.10
1995-96 1.68 1.27 0.56 0.10 0.37 0.61 0.23 -
1996-97 1.20 1.20 0.34 0.54 0.90 0.99 1.59 2.64
1997-98 1.74 1.43 0.77 1.21 2.65 1.90 2.51 1.62
1998-99 1.09 1.24 0.31 1.36 1.43 0.47 1.97 2.24
1999-00 1.02 1.24 0.48 0.85 0.82 1.42 2.27 0.47
2000-01 0.62 0.40 -0.09 0.43 1.42 1.70 2.47 0.33
2001-02 0.95 0.36 0.46 0.75 1.05 0.66 1.24 1.84
2002-03 1.28 0.30 0.58 0.94 0.89 1.56 1.96 0.74
2003-04 1.55 1.00 1.25 0.82 0.35 -0.37 0.61 -0.11
2004-05 0.60 0.80 0.20 0.69 0.23 1.63 3.39 2.43
2005-06 1.23 1.59 0.89 1.12 0.89 1.33 1.15 0.97
2006-07 1.08 1.08 -0.04 0.43 0.56 1.35 2.00 0.84
2007-08 0.60 0.06 -0.28 0.43 0.44 1.35 -0.64 2.25
2008-09 0.99 0.51 0.75 0.46 0.74 1.48 2.08 4.73
2009-10 1.95 1.13 0.88 0.53 0.97 1.16 2.50 0.79
2010-11 1.53 0.41 -0.19 0.08 0.43 0.76 1.73 -0.10
2011-12 1.59 0.11 0.61 0.50 0.56 0.63 0.97 -0.79
2012-13 1.34 0.87 0.79 0.27 0.80 0.34 0.80 1.40
2013-14 1.02 0.25 0.56 0.32 -0.05 -0.40 0.67 0.58
2014-15 1.32 1.40 0.71 -0.29 0.97 0.46 0.98 1.15
2015-16 0.70 0.74 -0.11 0.48 0.67 -0.06 0.17 -0.55
2016-17 1.09 1.43 0.44 1.51 0.74 0.84 0.99 1.59
2017-18 1.11 0.83 0.44 0.47 -0.03 1.27 0.98 1.81
2018-19 1.22 0.44 0.59 0.56 1.35 0.65 1.67 1.59
2019-20 1.96 0.98 0.61 0.64 0.81 1.03 0.44 1.04
2020-21 1.48 0.89 0.88 0.80 1.64 1.80 2.15 2.58
2021-22 1.30 0.72 0.24 0.36 0.84 0.75 1.77 1.86
Table 6.9. HADDOCK. Survey mortality from surveys in the Barents Sea standard area winter 1994-2022.

6.4 - Growth and maturity

Tables 6.10 and 6.11 present the time series for mean length and mean weight at age. Length and weight estimates have been variable with no specific trends in the latest years. Lengths in 2022 were below average for ages 1-2 and 5-7 but above average for older fish, while mean weights were below average for ages 1 and 4-7 and above average for older fish. Annual weight increments are shown in Table 6.12, these are highly variable and show no trends. The proportion mature at age also shows large variations between years (Table 6.13). The large variation is one of the reasons that length, weight and maturity at age are modelled from the empirical data in the haddock stock assessment to account for inconsistencies due to high sampling variance and to fill in missing age-year combinations. The assessment input data for these variables may therefore differ somewhat from tables 6.10, 6.11 and 6.13.

The degree of coverage of the Russian EEZ may influence the biological parameters, as body size tends to decrease towards the northeast in the survey area. In addition, length, weight and maturity at age of older ages has higher uncertainty due to fewer samples (c.f. table 2.3).

Age/ Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1994 14.5 19.9 29.3 38.1 47.8 54.0 61.0 64.3 70.4 64.8 64.1 + - -
1995 15.1 18.2 28.6 34.0 42.8 51.3 58.9 + + + - + + -
1996 15.3 20.8 28.0 36.9 41.2 47.2 55.0 59.9 - + - + + -
1997 15.7 19.7 27.4 34.1 39.5 47.3 50.7 55.0 62.8 - - - + +
1998 14.5 22.5 29.3 37.3 43.1 48.4 52.1 53.3 58.2 + + - - -
1999 14.4 18.3 32.3 38.8 46.5 51.9 56.0 55.2 58.8 + - + - -
2000 15.5 21.6 29.9 42.0 47.0 51.1 53.4 59.1 59.3 62.0 + + + -
2001 14.6 22.1 32.1 37.6 48.0 50.4 59.1 56.2 64.6 66.5 68.2 + + -
2002 15.1 20.8 29.1 39.8 45.2 51.7 57.8 60.7 + + 64.6 68.0 + -
2003 15.8 23.9 26.4 36.6 45.8 49.7 54.8 60.9 63.9 61.6 67.3 + + -
2004 14.2 22.1 30.1 35.7 42.8 49.8 49.8 59.0 63.0 73.5 75.9 + + 74.1
2005 14.8 20.5 29.9 36.1 40.5 48.3 51.6 55.7 60.8 + - - - -
2006 14.5 22.0 30.7 37.9 43.3 47.3 50.7 56.7 60.4 + - + - -
2007 15.5 22.9 29.0 35.7 45.8 48.0 53.5 57.4 57.3 68.7 + - - -
2008 15.7 23.8 29.6 37.8 42.8 46.5 53.1 53.8 59.5 + + + - -
2009 14.3 22.3 29.7 35.5 41.7 48.1 49.7 56.5 + 62.8 - + - -
2010 14.4 19.9 30.8 36.9 41.1 45.3 49.7 58.9 59.4 62.0 + + - -
2011 13.6 23.2 28.5 39.4 42.9 46.1 48.3 62.5 53.8 - - + + -
2012 14.7 19.3 31.6 35.1 43.6 47.1 50.1 51.2 53.4 65.3 + 71.7 - -
2013 14.5 22.9 30.0 40.9 42.8 48.7 52.2 52.9 55.7 67.3 - - - -
2014 15.4 18.5 31.9 38.4 46.4 52.4 53.6 55.3 55.2 61.0 58.9 - - +
2015 14.5 20.4 26.2 39.8 45.7 52.5 53.6 57.5 57.0 59.9 59.9 67.3 + -
2016 14.9 18.4 30.9 36.8 47.8 53.1 56.0 58.6 61.1 60.4 60.1 63.6 - +
2017 15.8 20.5 30.5 40.0 49.6 52.9 56.1 60.6 61.2 63.2 62.5 64.7 67.3 -
2018 14.5 21.7 30.4 39.6 47.8 54.4 58.0 61.3 64.2 65.6 64.6 63.9 66.5 68.9
2019 14.8 21.5 29.7 37.1 46.1 52.5 53.6 60.5 64.3 65.7 67.5 67.3 69.5 69.3
2020 15.4 21.9 30.0 36.3 42.7 52.1 57.4 62.2 63.7 68.1 69.7 67.4 69.0 70.3
2021 14.4 19.5 29.1 36.2 42.7 49.2 55.0 60.5 66.7 69.4 73.0 71.6 71.7 +
2022 14.1 20.2 31.2 37.4 42.6 47.1 51.6 61.4 65.0 68.5 69.0 - - +
Table 6.10. HADDOCK. Mean length (cm) at age from bottom trawl surveys in the Barents Sea standard area winter 1994-2022. Bootstrap mean estimates. “+” indicates few samples (< 3), while “–“ indicates no samples. Lengths are not adjusted for incomplete coverage.
Age/ Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1994 25 85 244 539 1060 1599 2146 2719 3349 2722 2662 + - -
1995 30 69 219 382 775 1357 1954 + + + - 2537 + -
1996 32 92 218 473 669 1022 1627 1948 - + - + 3626 -
1997 35 82 193 381 616 1051 1300 1680 2476 - - - + +
1998 27 113 247 543 863 1166 1417 1583 2046 + + - - -
1999 28 77 334 580 1020 1445 1775 1730 2020 + - + - -
2000 33 109 275 736 1050 1367 1586 2093 2219 2575 + + + -
2001 28 106 337 582 1146 1422 2140 2029 2939 3139 3105 + + -
2002 30 85 244 621 923 1388 1927 2242 + + 2692 3280 + -
2003 36 128 192 492 959 1204 1534 1982 2580 2675 3179 + + -
2004 23 98 271 458 752 1162 1222 1978 2611 3875 4186 + + 4036
2005 29 97 263 471 669 1087 1376 1881 2120 + - - - -
2006 26 109 301 559 812 1086 1362 1925 2075 + - + - -
2007 32 109 253 519 1016 1193 1718 2043 2258 3443 + - - -
2008 32 114 247 551 835 1115 1573 1599 2167 + + + - -
2009 26 94 227 444 746 1147 1315 1732 + 2567 - + - -
2010 28 87 275 473 677 957 1261 1889 2204 2492 + + - -
2011 21 117 220 520 729 943 1171 2264 1641 - - + + -
2012 29 75 306 432 819 1015 1280 1313 1700 2693 + 3287 - -
2013 25 114 272 645 782 1138 1351 1502 1850 3117 - - - -
2014 32 68 352 589 1002 1428 1566 1674 1704 2212 2156 - - +
2015 23 88 200 590 885 1418 1501 1915 1848 2085 2298 3148 + -
2016 27 74 285 495 1058 1466 1754 2089 2290 2263 2402 2716 - +
2017 33 95 293 637 1247 1542 1822 2294 2420 2640 2633 2890 3241 -
2018 26 95 275 627 1051 1663 1967 2349 2699 2820 2681 2648 3011 3415
2019 25 90 242 510 968 1411 1618 2083 2722 2916 3072 3220 3475 3229
2020 27 89 244 458 806 1385 1863 2426 2658 2887 3334 3013 3366 3600
2021 27 86 208 447 735 1159 1591 2201 3156 3172 3835 3533 3771 +
2022 24 96 292 478 731 1027 1386 2316 2774 3052 3357 - - +
Table 6.11. HADDOCK. Mean weight (g) at age from bottom trawl surveys in the Barents Sea standard area winter 1994-2022. Bootstrap mean estimates. “+” indicates few samples (< 3), while “–“ indicates no samples. Weights are not adjusted for incomplete coverage.
Year\Age 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10
1994-95 44 134 137 235 297 355 - - -
1995-96 61 148 253 287 247 270 -5 - -
1996-97 50 101 164 143 382 278 53 528 -
1997-98 78 165 349 481 550 366 283 366 -
1998-99 50 221 333 478 582 609 313 437 -
1999-00 81 198 403 470 347 141 318 489 554
2000-01 74 227 308 409 372 773 444 846 920
2001-02 57 138 285 341 242 505 102 - -
2002-03 98 106 248 338 281 146 54 338 -
2003-04 62 143 267 261 203 18 444 629 1295
2004-05 74 165 200 210 335 214 660 142 -
2005-06 80 204 296 341 417 275 550 194 -
2006-07 84 144 218 457 381 632 681 333 1368
2007-08 82 138 298 316 99 380 -119 124 -
2008-09 62 113 197 196 311 199 160 - 400
2009-10 61 181 246 233 211 115 574 472 -
2010-11 89 133 245 256 266 214 1003 -248 -
2011-12 53 189 212 299 285 337 142 -565 1052
2012-13 85 197 339 349 319 336 221 537 1418
2013-14 43 238 317 357 646 428 323 202 362
2014-15 56 132 238 296 416 73 348 175 381
2015-16 51 197 295 468 580 337 588 375 414
2016-17 68 219 352 753 483 356 540 331 350
2017-18 61 180 334 414 416 426 527 405 400
2018-19 64 148 235 341 361 -45 116 373 217
2019-20 64 155 216 296 417 452 808 575 165
2020-21 58 120 202 278 350 199 337 733 519
2021-22 69 206 270 284 292 227 725 573 -104
Table 6.12. HADDOCK. Yearly weight increment (g) from bottom trawl surveys in the Barents Sea standard area winter 1994-2022.
Age/ Year 1 2 3 4 5 6 7 8 9 10 11 12 13 14
1994 0.00 0.00 0.00 0.02 0.16 0.41 0.44 1.00 0.88 0.74 0.74 + - -
1995 0.00 0.00 0.01 0.04 0.18 0.38 0.41 + + + - 0.63 + -
1996 0.00 0.00 0.00 0.04 0.08 0.27 0.40 0.78 - + - + 0.00 -
1997 0.00 0.00 0.00 0.00 0.15 0.33 0.64 0.31 0.70 - - - + +
1998 0.02 0.00 0.00 0.04 0.15 0.54 0.50 0.79 0.95 + + - - -
1999 0.00 0.00 0.00 0.06 0.24 0.38 0.77 0.81 0.98 + - + - -
2000 0.00 0.00 0.00 0.24 0.54 0.66 0.82 1.00 0.90 0.86 + + + -
2001 0.00 0.00 0.00 0.22 0.54 0.49 0.89 1.00 1.00 0.70 1.00 + + -
2002 0.00 0.00 0.01 0.12 0.45 0.60 0.95 0.90 + + 0.79 1.00 + -
2003 0.00 0.00 0.00 0.04 0.40 0.59 0.73 0.60 0.64 0.68 1.00 + + -
2004 0.00 0.00 0.02 0.03 0.14 0.61 0.56 0.46 0.87 1.00 1.00 + + 1.00
2005 0.00 0.00 0.01 0.06 0.19 0.43 0.76 0.34 1.00 + - - - -
2006 0.00 0.00 0.00 0.12 0.41 0.59 0.84 0.86 0.50 + - + - -
2007 0.00 0.00 0.01 0.19 0.46 0.67 0.82 0.95 0.84 1.00 + - - -
2008 0.13 0.02 0.02 0.09 0.47 0.66 0.83 0.84 0.99 + + + - -
2009 0.00 0.00 0.00 0.04 0.16 0.29 0.64 0.65 + 0.41 - + - -
2010 0.00 0.00 0.05 0.08 0.20 0.41 0.60 0.75 0.91 0.89 + + - -
2011 - 0.00 0.00 0.07 0.14 0.41 0.38 0.38 0.79 - - + + -
2012 0.00 0.00 0.01 0.06 0.38 0.51 0.61 0.71 0.26 1.00 + 0.68 - -
2013 0.00 0.00 0.01 0.04 0.17 0.49 0.61 0.62 0.63 1.00 - - - -
2014 0.00 0.01 0.02 0.13 0.28 0.73 0.73 0.71 0.76 0.94 0.95 - - +
2015 0.00 0.00 0.03 0.05 0.15 0.44 0.64 0.67 0.39 0.54 1.00 0.68 + -
2016 0.00 0.00 0.00 0.02 0.32 0.70 0.83 0.82 0.89 0.83 0.94 1.00 - +
2017 0.00 0.00 0.01 0.15 0.32 0.63 0.74 0.95 0.93 0.97 0.98 1.00 1.00 -
2018 0.00 0.00 0.01 0.12 0.31 0.55 0.87 0.76 0.93 0.84 0.86 0.93 0.94 1.00
2019 0.00 0.00 0.02 0.08 0.18 0.59 0.66 0.83 0.92 0.97 1.00 1.00 1.00 1.00
2020 0.00 0.00 0.01 0.04 0.18 0.56 0.75 0.82 0.91 0.89 0.98 1.00 0.89 0.93
2021 0.00 0.00 0.00 0.06 0.14 0.47 0.64 0.73 0.81 1.00 1.00 0.79 0.88 +
2022 0.00 0.00 0.08 0.05 0.18 0.50 0.79 0.66 0.51 0.49 0.84 - - +
Table 6.13. HADDOCK. Proportion mature at age from bottom trawl surveys in the Barents Sea standard area winter 1994-2022. Bootstrap mean estimates. The proportion mature is the number of fish classified as maturity category 2 and 3, divided by the total number of fish assigned categories 1-5. “+” indicates few samples (< 3), while “–“ indicates no samples.

7 - Distribution and abundance of redfish

Earlier reports from this survey have presented distribution maps and abundance indices based on acoustic observations of redfish. In later years, blue whiting has dominated the acoustic records in some of the main redfish areas. Due to incomplete pelagic trawl sampling the splitting of acoustic records between blue whiting and redfish has been very uncertain. The uncertainty relates mainly to the redfish, since it only makes up a minor proportion of the total value. This has been the case since the 2003 survey, and the acoustic results for redfish are therefore not included in the reports.

7.1 - Golden redfish (Sebastes norvegicus)

Figure 7.1 shows the geographical distribution of golden redfish based on the catch rates in bottom trawl. In most years, the distribution is completely covered except towards the northwest. Table 7.1 presents the time series (1994-2022) of swept area indices by 5 cm length groups for the standard area (strata 1-23). The indices were low in many years since 1999 for all length groups. However, in 2016 and 2017 there was an increase in the indices of fish above 25 cm, and in 2018 the total index was at the same level as in 2017, while the total biomass was slightly lower. In 2019 the indices for fish between 35 and 50 cm increased further, and the total abundance and biomass were the highest since 1998. The index for most length groups declined in 2020 and further in 2021 when the abundance of fish < 20 cm was particularly low. In 2022 fish > 20 cm increased, but the total abundance and biomass had decreased. Table 7.2 present swept area abundance indices by length groups for area N in 2014-2022. Golden redfish was found in this extended survey area in 2014-2022, mainly west of Spitsbergen (strata 24). 16% of the total abundance and 5 % of total biomass was found in the extended area in 2022.

 

GOLDEN REDFISH (Sebastes norvegicus). Distribution in the trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 7.1. GOLDEN REDFISH ( Sebastes norvegicus) . Distribution in the trawl catches winter 2022 (number per nm 2 ). Black crosses indicate zero catches and the stippled line the ice edge.

Table 7.3 presents estimates of coefficients of variation (%) by length groups. In all years, CVs for most length groups are above what could be considered as acceptable in stock assessment (approximately 20 %).

 

  Length group (cm)         Biomass
Year 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60 Total (tons)
1994 675 7493 10100 12840 10914 17834 10065 4799 1645 937 202 121 77623 31841
1995 387 4658 13515 13118 10398 15429 16223 10587 3112 852 455 148 88883 42151
1996 40 715 3291 5983 8863 14089 15709 7502 2692 893 168 165 60010 35775
19971 0 500 1197 2809 6522 22751 28797 8235 1747 1092 239 97 73985 44977
19981 51 4525 2043 10795 73085 30862 14707 6984 1712 456 142 0 145363 49253
1999 181 928 2070 4002 4351 6275 6143 5474 2618 738 75 0 32854 20330
2000 533 1122 1506 4196 4895 5146 3611 1908 620 466 89 0 24092 10946
2001 55 411 398 2452 5802 5463 4509 3239 1154 343 96 37 23960 13896
2002 133 1053 2043 1854 3955 4204 3335 3654 1656 619 192 28 22726 13242
2003 0 478 1303 1538 4192 4081 2765 3204 1996 548 123 327 20554 13399
2004 700 195 420 973 2842 4365 5404 3858 2281 562 140 45 21786 15758
2005 0 119 203 362 1110 2090 3849 4664 2730 1276 299 128 16831 16389
20062 0 0 0 178 2495 5534 6307 4155 3179 950 124 12 22934 18790
20071 0 97 453 214 772 1526 2823 4275 2742 1194 197 58 14351 14553
2008 1736 2540 201 171 440 710 1969 2547 3049 1231 157 19 14768 12647
2009 0 0 86 0 39 436 1745 3779 4200 1959 267 101 12728 17237
2010 372 2017 1168 527 136 60 833 1062 2073 1596 205 128 10175 9787
2011 342 3187 2068 288 402 125 274 2329 3030 1912 131 243 14332 13302
20123 805 4375 3995 1835 550 316 881 3645 4083 1775 320 85 22664 16011
2013 75 7418 4896 3952 1550 355 878 821 1284 1594 384 451 23658 11456
2014 128 1043 1440 3005 3363 1023 507 1427 2139 1176 633 193 16077 12087
2015 139 881 1467 3019 2603 2013 458 720 1237 1216 874 82 14710 10120
2016 748 1291 1484 2396 4290 3673 3391 1658 2147 2307 1114 250 24749 19847
20173 341 1304 898 1065 4462 9060 6661 2980 2087 1776 604 498 31735 25050
2018 1129 2750 1799 1678 3282 4693 6335 4323 2012 1630 715 299 30645 22871
2019 671 3248 1700 2409 2515 3910 9024 9693 6709 1544 477 415 42279 36241
20203 971 650 1498 1041 1891 2424 6450 8786 6426 2773 503 151 33496 33564
20213 43 303 872 1172 1093 1523 4090 5938 5323 2753 1190 239 24539 29317
2022 1708 1732 432 832 1727 1311 4696 4740 3610 1534 476 187 22986 21175
Table 7.1. GOLDEN REDFISH (Sebastes norvegicus). Abundance indices (numbers in thousands) from bottom trawl surveys in the Barents Sea standard area winter 1994-2022.

1 Indices raised to also represent the Russian EEZ

2 Not complete coverage in southeast due to restrictions, strata 7 area set to default and strata 13 as in 2005

3 Indices not raised to also represent uncovered parts of the Russian EEZ.

  Length group (cm)   Biomass
Year 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45 Total (tons)
2014 35 333 358 1440 2594 1315 211 501 379 7166 2913
2015 0 202 197 127 804 804 363 0 154 2651 1261
2016 0 0 103 300 597 1186 828 107 32 3151 1405
2017 0 66 93 587 519 679 547 96 66 2654 1053
2018 58 824 750 647 639 964 1855 546 50 6331 2598
2019 76 974 1445 567 666 1445 1043 519 102 6838 2525
2020 37 277 1239 934 1315 2498 2027 993 375 9695 4850
2021 25 305 1051 1173 437 893 857 389 126 5256 2004
2022 25 167 322 1127 1233 357 366 50 47 3694 1109
Table 7.2. GOLDEN REDFISH (Sebastes norvegicus). Abundance indices (numbers in thousands) for new strata 24-26 from bottom trawl surveys in the Barents Sea winter 2014-2022.
  Length group (cm)    
Year 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59
1994 49  38  23  29  21  37  20  34  15  18  35 
1995 46  41  34  29  19  34  31  33  24  25  42 
1996 73  51  48  27  18  29  27  22  17  24  46 
19971 -   39  26  24  19  60  66  34  16  20  35 
19981 53  30  27  27  24  38  44  42  24  27  44 
1999 63  41  37  38  35  27  36  58  56  26  58 
2000 35  28  19  24  22  28  30  29  20  23  58 
2001 56  32  25  26  33  31  40  52  28  27  43 
2002 56  61  52  24  27  22  25  33  37  25  41 
2003 -   28  34  34  24  23  14  19  26  38  76 
2004 72  38  30  28  33  55  53  26  23  26  50 
2005 -   73  48  36  20  26  29  17  19  26  65 
20062 -   -   -   53  48  42  32  29  22  20  43 
20071 -   70  61  57  29  22  24  24  22  20  34 
2008 33  27  39  63  38  23  21  25  19  25  49 
2009 -   -   69  -   67  31  31  25  25  22  37 
2010 57  27  46  48  41  54  32  29  18  20  35 
2011 43  40  24  45  31  49  39  67  43  38  50 
20122 35  42  23  22  37  39  24  42  46  31  39 
2013 57  43  23  17  23  46  42  39  32  23  42 
2014 53  32  28  17  20  38  37  37  27  24  24 
2015 66  39  32  30  19  19  23  38  26  22  33 
2016 49  31  19  18  24  18  18  28  22  21  31 
20172 98  42  41  27  29  61  33  32  27  35  29 
2018 33  21  17  20  19  17  22  17  21  21  25 
2019 39  26  18  -   18  18  20  31  32  19  34 
20202 84  26  24  22  22  32  31  45  33  29  43 
20212 70  28  18  17  21  30  37  40  42  35  37 
2022 45  69  31  22  23  23  29  29  23  24  32 
Table 7.3. GOLDEN REDFISH (Sebastes norvegicus). Estimates of coefficients of variation (%) for swept area abundance indices. Barents Sea standard area winter 1994-2022.

1 Russian EEZ not covered

2 Russian EEZ partly covered

7.2 - Beaked redfish (Sebastes mentella)

Figure 7.2 shows the geographical distribution of beaked redfish based on the catch rates in bottom trawl. Table 7.4 presents the time series (1994-2022) of swept area abundance indices by 5 cm length group for beaked redfish in the standard area (strata 1-23), while table 7.5 present indices for new strata 24-26 in 2014-2022.   

In 2015 and 2016, the estimated indices for 20-39 cm beaked redfish were among the highest in the time series, and in 2017 the indices for 30-39 cm beaked redfish were the highest in the time series, as were the total index and total biomass. The indices for most length groups decreased somewhat from 2017 to 2018 and remained at about the same level in 2019 and 2020 before decreasing further in 2021. However, the 2020 year class, appears to have been strong as the 2021 estimate of fish < 10 cm and 2022 estimate of <14 cm fish were the highest in the time series. The coverage of the beaked redfish distribution was not complete west and north of Spitsbergen (Fig. 7.2). The extended survey area contributed about 5% of the total abundance index, compared to around 3 % in 2019 and 2020 and 10 % in 2021.   

Table 7.6 presents estimates of coefficients of variation (%) by length groups. In most years, CVs for length groups between 10 and 29 cm are at a level that could be considered as acceptable for stock assessment, and in most recent years up to 44 cm.  

 

GOLDEN REDFISH (Sebastes norvegicus). Distribution in the trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 7.2. BEAKED REDFISH (Sebastes mentella). Distribution in the trawl catches winter 2022 (number per nm 2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

  Length group (cm)  
Year 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45 Total Biomass (‘000 t)
1994 8  296  479  488  74  74  17  3  0  1440  161 
1995 310  84  571  390  83  58  24  3  0  1522  152 
1996 215  101  198  343  136  42  17  1  0  1053  128 
19972 38  83  19  198  266  82  39  3  0  728  166 
19982 1  87  62  101  202  40  13  2  0  507  96 
1999 2  7  70  37  172  73  22  3  0  386  102 
2000 9  13  40  78  143  97  27  7  1  415  113 
2001 10  23  7  57  79  75  10  1  0  260  65 
2002 17  7  19  36  96  116  24  1  0  317  90 
2003 4  4  10  13  70  198  46  6  0  351  138 
2004 2  3  7  19  33  86  32  2  0  183  68 
2005 0  6  7  11  28  154  86  4  0  296  131 
20063 100  2  10  15  23  104  83  3  1  339  108 
20072 382  121  3  7  12  121  121  7  0  773  136 
2008 858  359  27  5  12  104  165  5  0  1533  169 
2009 95  325  136  5  9  67  163  6  0  806  156 
2010 652  276  215  64  7  74  191  6  0  1485  190 
2011 501  230  212  149  14  47  157  5  0  1315  177 
20124 129  280  86  125  47  14  154  18  0  855  173 
2013 249  227  245  159  143  35  193  27  0  1279  247 
2014 91  174  250  114  125  51  115  14  0  933  171 
2015 175  110  215  302  290  215  171  18  0  1495  343 
2016 615  105  149  332  213  163  124  14  0  1714  264 
20175 568  185  68  197  286  310  231  11  0  1855  412 
2018 189  250  83  109  192  270  214  22  1  1329  350 
2019 42  288  263  92  158  255  211  20  0  1330  339 
20204 196  122  207  92  118  231  209  25  1  1200  313 
20214 887  132  142  124  81  186  172  23  1  1749  277 
2022 616  981  54  112  76  87  152  20  0  2098  224 
Table 7.4. BEAKED REDFISH (Sebastes mentella)1. Abundance indices (numbers in millions) from bottom trawl surveys in the Barents Sea standard area winter 1994-2022.

1 Includes unidentified Sebastes specimens, mostly less than 10cm

2 Indices raised to also represent the Russian EEZ

3 Not complete coverage in southeast due to restrictions, strata 7 area set to default and strata 13 as in 2005

4 Indices not raised to represent uncovered parts of the Russian EEZ

5 Indices raised to also represent uncovered parts of the Russian EEZ

  Length group (cm)   Biomass
Year 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 >45 Total (‘000 t)
2014 19.6  9.2  11.5  6.8  5.4  1.7  2.3  0.4  0  56.9  5.5 
2015 13.5  5.5  8.3  11.3  11.4  5.2  3.4  0.1  0.03  58.9  9.4 
2016 54.6  3.1  2.2  4.5  4.8  4.2  1.4  0.3  0  75.0  4.5 
2017 81.9  13.1  1.3  4.5  6.0  6.4  3.6  0.6  0.03  117.4  7.8 
2018 47.9  74.0  2.3  1.8  4.6  5.9  5.8  0.6  0  143.0  8.6 
2019 10.9  10.1  7.0  0.7  1.4  1.3  2.1  0.2  0.03  33.7  3.0 
2020 12.8  3.1  4.5  1.7  2.0  7.3  4.9  0.6  0.04  36.8  7.9 
2021 136.1  1.0  4.3  6.0  3.2  15.2  9.4  0.5  0.05  175.7  14.5    
2022 110.2  53.2  1.3  4.3  2.0  5.6  6.8  0.4  0  183.7  9.7 
Table 7.5. BEAKED REDFISH (Sebastes mentella)1. Abundance indices (numbers in millions) for new strata 24-26 from bottom trawl surveys in the Barents Sea winter 2014-2022.

1 Includes unidentified Sebastes specimens, mostly less than 10cm

  Length group (cm)
Year 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45  
1994 36  14  29  34  27  24  28  49  59   
1995 17  26  23  22  16  17  23  33  37   
1996 17  22  28  19  16  33  24  38  63   
19972 20  19  18  15  16  18  24  60  95   
19982 33  16  20  14  19  18  23  32  71   
1999 20  17  15  13  20  23  27  53  71   
2000 15  12  15  14  16  22  31  69  85   
2001 15  14  15  13  14  18  16  25  69   
2002 53  13  13  19  17  20  17  25  67   
2003 54  15  17  17  17  28  29  46  90   
2004 19  16  15  19  14  14  18  19  56   
2005 -   25  18  16  17  19  22  38  42   
20063 13  50  26  30  19  19  17  21  79   
20072 15  24  18  15  15  23  18  40  60   
2008 12  15  25  17  16  21  20  25  45   
2009 12  10  16  21  36  31  25  22  51   
2010 14  11  10  14  20  33  32  20  88   
2011 12  11  11  15  19  34  26  23  58   
20124 15  12  14  15  19  29  37  56  45   
2013 20  18  34  20  26  29  28  29  51   
2014 10  11  11  12  17  19  28  24  51   
2015 13  12  12  16  24  22  19  32  43   
2016 10  10  14  22  18  16  19  18  60   
20175 9  13  15  14  14  15  16  17  81   
2018 10  11  12  14  11  13  17  23  33   
2019 11   12   15   12   16   18   19   21   59    
20204 11  14  11  11  15  13  12  17  49   
20214 13  32  11  15  18  24  19  19  49   
2022 -   -   16  14  13  12  14  18  61   
Table 7.6. BEAKED REDFISH (Sebastes mentella)1. Estimates of coefficients of variation (%) for swept area abundance indices. Barents Sea standard area winter 1994-2022.

1 Includes unidentified Sebastes specimens, mostly less than 10cm

2 Russian EEZ not covered

3 Russian EEZ partly covered

7.3 - Norway redfish (Sebastes viviparus)

Figure 7.3 shows the geographical distribution of Norway redfish and Table 7.7 presents the time series (1994-2022) of swept area indices by 5 cm length groups in the standard area (strata 1-23). Almost all Norway redfish are found in areas ABCD, mainly in main area B, and almost nothing in the extended survey area (Table 7.8). In 2021, the smallest fish (< 10 cm) were found in the extended survey area for the first time and then again in 2022 as the < 15 cm fish.  

A few large catches often drive the indices for Norway redfish. There was a large and unexplained increase in the indices of most length groups from 2013 to 2015 to among the highest levels in the time series. Apart from a dip in 2016, the total abundance has remained relatively high since then. The total abundance increased with nearly 50 % in 2021 to the highest observed since 1994, driven by high abundance of 15-30 cm fish. In 2022 however, the abundance of <10 cm increased significantly, while the other length groups decreased.  

Table 7.9 presents estimates of coefficients of variation (%) by length groups. In most years, CVs for most length groups are far above what could be considered as acceptable for stock assessment.  

 

NORWAY REDFISH (Sebastes viviparus). Distribution in the trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 7.3. NORWAY REDFISH ( Sebastes viviparus) . Distribution in the trawl catches winter 2022 (number per nm 2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

  Length group (cm)  
Year 5-9 10-14 15-19 20-24 25-29 30 Total
1994 75355  94809  17218  12818  1377  279  201857 
1995 10716  68713  22737  9349  3306  503  115325 
1996 439  45796  43673  35921  5498  87  131415 
19971 898  24202  28857  18768  4397  0  77122 
19981 703  9385  42183  20801  2939  91  76102 
1999 1577  10134  11675  2921  707  35  27049 
2000 953  4904  37128  21976  2086  133  67179 
2001 249  2243  30082  34425  3802  120  70921 
2002 311  3223  17485  15028  1265  84  37395 
2003 234  4306  22603  31019  4277  167  62605 
2004 102  1793  24461  32768  3294  291  62709 
2005 172  1582  16443  37359  6153  356  62066 
20062 819  4480  3653  10381  2244  205  21782 
20071 704  5238  15652  34395  2448  80  58517 
2008 0  1820  5906  21010  4557  29  33322 
2009 506  528  3096  11032  3405  419  18987 
2010 1704  454  10134  53180  7571  22  73065 
2011 533  1250  2168  7757  2197  106  14011 
20121 586  3950  4080  29157  6212  74  44059 
2013 1210  9521  3300  23464  8544  100  46139 
2014 11388  17753  21079  64094  15135  1991  131439 
2015 7353  27428  30881  65883  9178  115  140839 
2016 2795  26824  18396  29229  11286  934  89464 
20171 3848  58422  21556  22580  5685  426  112518 
2018 787  24370  61427  37470  26220  1344  151617 
2019 730  14679  58705  31991  6469  1250  113824 
20201 603  3485  58704  46850  15290  907  125840 
20211 1205  8858  82510  74590  19302  677  187141 
2022 2001  2858  38592  52312  1914  300  98336 
Table 7.7. NORWAY REDFISH (Sebastes viviparus). Abundance indices (numbers in thousands) from bottom trawl surveys in the Barents Sea standard area winter 1994-2022.

1 Indices not raised to represent the Russian EEZ or uncovered parts, Sebastes viviparus is mainly found in Norwegian EEZ

2 Not complete coverage in southeast due to restrictions, strata 7 area set to default and strata 13 as in 2005

  Length group (cm)  
Year 5-9 10-14 15-19 20-24 25-29 30 Total
2014 0 87 44 0 0 0 131
2015 0 0 35 0 0 0 35
2016 0 0 111 0 0 0 111
2017 0 0 0 0 0 0 0
2018 0 0 160 126 32 0 318
2019 0 0 51 0 0 0 51
2020 0 0 54 54 0 0 108
2021 51 0 0 74 0 0 125
2022 0 75 29 27 0 0 131
Table 7.8. NORWAY REDFISH ( Sebastes viviparus). Abundance indices (numbers in thousands) for new strata 24-26 from bottom trawl surveys in the Barents Sea winter 2014-2022.
  Length group (cm)
Year 5-9 10-14 15-19 20-24 25-29 30-34
1994 41  55  28  40  43  67 
1995 49  36  48  39  78  98 
1996 67  23  31  36  47  65 
19971 83  37  32  53  59  -  
19981 41  25  46  73  78  78 
1999 80  59  33  24  36  65 
2000 54  32  45  44  38  55 
2001 39  26  31  29  34  90 
2002 62  38  20  24  40  85 
2003 71  35  36  32  28  75 
2004 53  38  36  33  25  69 
2005 63  33  38  31  34  67 
20062 73  72  21  27  25  59 
20071 71  76  34  36  31  87 
2008 -   53  30  30  41  74 
2009 67  48  26  27  30  63 
2010 47  37  48  53  57  98 
2011 51  51  45  39  42  74 
20122 44  28  41  41  39  99 
2013 57  31  24  41  48  101 
2014 40  34  39  39  43  78 
2015 35  27  30  42  43  71 
2016 41  32  31  27  24  55 
20172 53  63  27  31  29  53 
2018 46  47  35  47  35  64 
2019 60  60  47  33  27  73 
20202 64  30  40  41  59  48 
20212 50  32  44  43  45  74 
2022 64  37  43  -  -  - 
Table 7.9. NORWAY REDFISH ( Sebastes viviparous). Estimates of coefficients of variation (%) for swept area abundance indices. Barents Sea standard area winter 1994-2022.

1 Russian EEZ not covered

2 Russian EEZ partly covered

8 - Distribution and abundance of Greenland halibut

Figure 8.1 shows the distribution of bottom trawl catch rates of Greenland halibut. The most important distribution areas for the adult fish (depths between 500 and 1000 m along the western slope), are not covered by the survey. The observed distribution pattern in 2022 was similar to those observed in previous years’ surveys. However, in 2022 some trawling was also performed in or close to the ice in the central Barents Sea (stratum 26), revealing large concentrations of Greenland halibut < 35 cm in this area.

 

GREENLAND HALIBUT. Distribution in the trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 8.1 GREENLAND HALIBUT. Distribution in the trawl catches winter 2022 (number per nm2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

The time series (1994-2022) of swept area abundance indices by 5 cm length groups in the standard area is presented in Table 8.1. Abundance indices have been low in the whole period, with few signs of improved recruitment in the covered area. However, recruitment from more northern areas has led to an increase in abundance indices of length groups above 30 cm since about 2005. There was a large increase in the indices of most length groups between 30 and 79 cm from 2014 to 2015, and the total index was the highest in the time series back to 1994. After decreasing indices from 2016-2018, the 2019 indices of all length groups above 34 cm increased, and the total index and biomass were at the same level as in 2015 and among the highest in the time series. From 2020 there has been an increasing trend in abundance, particularly for individuals less than 50 cm. The index is now approaching an all-time high.

Table 8.2 presents swept area abundance indices by length groups for new strata 24-26 in 2014-2022. The index for 2021 and 2022 are much higher than in all previous years for individuals smaller than 35 cm, which is related to the coverage of areas close to/inside the ice that has not previously been covered in the survey.

Table 8.3 presents estimates of coefficients of variation (%) for length groups. In most years, only CVs for length groups between 40 and 59 cm are at a level that could be considered as acceptable for stock assessment.

  Length group (cm) Biomass (tons)
Year 14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80 Total
1994 0 0 21 76 148 1117 3139 4740 3615 1941 889 541 21 0 0 16248 19228
1995 298 0 0 0 90 129 2877 7182 5739 2027 1622 839 489 86 0 21378 27459
1996 4121 0 0 0 62 124 1214 4086 4634 1871 1112 638 337 74 12 18285 20256
1997 1 0 68 0 0 55 163 949 4313 5629 2912 1609 643 300 65 21 16728 24214
1998 1 68 220 945 578 481 487 1088 4016 6591 3076 1798 707 326 93 44 20518 27248
1999 43 84 241 436 566 269 784 1701 3097 1669 1094 491 89 75 0 10640 14681
2000 140 184 344 836 1722 3857 2253 1560 2144 1714 1191 615 249 76 0 16883 17246
2001 68 49 147 179 737 1525 3716 3271 2302 2010 1088 529 160 50 39 15871 18224
2002 271 0 70 34 382 1015 1916 3803 3250 2279 1138 976 242 159 114 15648 21198
2003 51 0 74 19 304 715 1842 3008 4765 2235 714 561 245 146 0 14678 19635
2004 106 104 15 0 319 1253 1229 1717 2277 1227 798 298 148 94 26 9615 11872
2005 263 70 159 1139 2235 2621 4206 3782 3847 2037 917 585 336 118 0 22314 22293
2006 2 0 72 94 414 1968 5149 4613 5743 4283 2132 891 449 258 34 18 26118 25579
2007 1 0 18 146 1869 1418 3114 5710 5947 4287 2205 963 658 391 80 89 26896 28006
2008 0 0 0 243 1708 5974 4654 6136 5198 3403 827 638 174 82 50 29088 30153
2009 55 0 0 26 1044 4327 8133 4551 4084 2266 996 627 442 253 154 26960 28919
2010 0 0 0 99 678 3648 5729 6560 4897 2467 1064 552 229 128 41 26092 25979
2011 51 0 0 0 216 4396 5864 5498 5237 3698 699 936 327 252 97 27271 31552
2012 3 2013 2014 77 0 0 0 0 0 0 0 46 0 0 92 51 0 156 1145 511 368 4524 5368 2271 5366 4868 5587 4517 5374 5903 2774 3687 3555 1147 1944 2251 195 939 1369 73 348 154 0 313 260 48 154 79 19917 23504 22090 22656 31748 31112
2015 367 0 61 0 284 1612 3187 6452 7249 6752 3350 1936 587 334 0 32172 46828
2016 205 0 124 511 950 1953 3486 4539 5479 5613 1999 1973 646 98 80 27657 35831
2017 4 52 0 0 78 592 1328 1885 3850 4852 4550 1721 1455 317 190 23 20827 29756
2018 0 0 62 0 383 1333 2049 3445 4258 3573 1904 1366 736 196 20 19325 28688
2019 0 0 0 375 272 1671 3285 4034 5177 4265 3570 2526 1328 535 137 27176 45912
2020 3* 80 91 246 442 790 2272 4391 5136 4929 4613 3278 1803 894 384 250 29599 43631
2021 3 0 154 927 927 2370 2976 3869 4265 3516 2991 2378 1649 670 682 238 27613 37090
2022 3 0 0 822 2165 3696 1831 3365 5322 5672 3621 2230 1543 799 432 135 31635 39584
Table 8.1 . GREENLAND HALIBUT. Abundance indices (numbers in thousands) from bottom trawl surveys in the Barents Sea standard area winter 1994-2022.

1 Indices raised to also represent the Russian EEZ

2 Not complete coverage in southeast due to restrictions, strata 7 area set to default and strata 13 as in 2005

3 Indices not raised to also represent uncovered parts of the Russian EEZ.

4 Indices raised to also represent uncovered parts of the Russian EEZ,

* The 2020 indices were updated in 2021 after an error was discovered in the calculations

  Length group (cm) Biomass (tons)
Year 14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80 Total
2014 2015 2016 0 0 678 134 0 933 141 0 607 0 269 436 138 30 336 453 263 431 1350 550 331 1443 863 728 1351 597 340 293 567 254 803 555 68 39 66 34 117 107 140 0 38 0 0 0 34 6261 3903 5349 7366 5092 3059
2017 31 0 0 193 583 861 662 456 301 33 298 30 0 34 0 3485 2990
2018 136 28 0 434 775 1840 1099 1042 776 634 360 511 0 0 0 7636 7528
2019 296 92 81 78 137 1072 1144 1384 896 649 638 297 24 40 0 6826 8118
2020 * 36 0 0 0 0 169 160 322 32 31 66 62 0 0 0 878 889
2021 1807 3961 3859 2159 1207 863 564 1612 1127 885 495 190 23 0 0 19704 10187
2022 263 0 1204 693 3157 3197 5502 5985 2057 868 337 280 87 0 0 23630 18191
Table 8.2 . GREENLAND HALIBUT. Abundance indices (numbers in thousands) for new strata 24-26 from bottom trawl surveys in the Barents Sea winter 2014-2022.

* The 2020 indices were updated in 2021 after an error was discovered in the calculations.

  Length group (cm)
Year 10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 65-69 70-74 75-79 80-84
1994 0 0 105 57 46 28 17 20 17 15 20 26 97 - -
1995 91 - - - 71 40 18 22 25 24 27 41 63 94 -
1996 33 - - - 69 45 22 25 18 19 36 29 40 58 -
1997 1 - 53 - - 82 48 26 23 18 16 16 24 28 73 101
1998 1 66 53 26 44 42 18 22 23 28 26 28 31 33 50 101
1999 91 54 53 26 32 31 24 21 18 16 18 25 52 51 -
2000 71 66 72 83 56 58 41 20 22 23 21 36 45 54 -
2001 92 99 85 47 40 48 44 46 37 14 17 34 43 56 -
2002 71 - 70 104 29 27 17 13 16 16 14 27 24 37 55
2003 66 - 63 95 30 27 20 44 34 32 44 28 38 37 -
2004 78 59 97 - 26 17 16 16 17 17 15 29 39 46 92
2005 66 70 37 46 33 15 19 17 16 20 25 24 28 64 -
2006 2 - 81 81 67 32 18 18 11 11 16 22 22 30 67 -
2007 1 - 99 52 23 20 13 12 12 14 14 24 37 26 44 99
2008 - - - 36 20 21 15 14 18 14 22 20 43 56 68
2009 98 - - 103 23 14 16 16 19 18 17 21 26 46 53
2010 - - - 57 26 18 13 12 14 18 19 23 45 57 101
2011 66 - - - 43 18 15 14 17 14 25 26 33 46 70
2012 2 93 - - - 100 23 13 14 14 11 24 70 72 - -
2013 - - - - - 44 39 12 16 20 19 33 50 50 -
2014 2015 2016 - 83 - - - - 99 99 101 68 - 50 68 49 43 37 24 31 20 22 21 14 15 34 20 13 26 18 18 31 18 34 16 24 37 20 53 33 36 51 46 70 72 - 98
2017 2 102 - - 72 42 25 23 13 14 17 21 26 45 65 95
2018 - - 107 - 51 24 15 18 18 15 17 23 32 54 93
2019 - - - 54 37 20 20 24 21 17 16 17 23 31 68
2020 2 90 73 101 62 42 21 14 14 14 15 14 15 24 51 51
2021 2 - 67 46 40 46 27 15 16 12 15 16 20 26 28 50
2022 - - 42 53 33 23 14 11 15 13 16 18 22 35 54
Table 8.3. GREENLAND HALIBUT. Estimates of coefficients of variation (%) for swept area abundance indices. Barents Sea standard area winter 1994-2022.

9 - Distribution and abundance of capelin, polar cod and blue whiting

9.1 - Capelin

Although capelin is primarily a pelagic species, small amounts of capelin are normally caught in the bottom trawl throughout most of the investigated area. In Figure 9.1 catch rates of capelin smaller and larger than 14 cm are shown for the winter survey in 2022. Catches in the south-eastern part of the survey area were lower than in previous years. Capelin smaller than 14 cm during this period will mainly comprise the immature stock component, while the larger capelin constitutes the pre-spawning capelin stock. Some few trawl hauls show large capelin catches (numbers exceeding 100 000 individuals), and these can probably not be considered representative for the density in the area, because such hauls will either result from hitting a capelin school at the bottom or up in the water column. For this reason, we choose not to present swept area-based indices for capelin in this report.

At this time of the year, mature capelin has started their approach to the spawning areas along the coast of Troms, Finnmark and the Kola peninsula, while immature capelin will normally be found further north and east, in the wintering areas. This is reflected on the maps of capelin distribution, even though some large capelin is always found north of 75°N, and smaller capelin are found sporadically in near-coastal areas. The geographical coverage of the total capelin stock is incomplete, but the maturing component is probably best covered.

It has been noted during several surveys that when sampling capelin from demersal and pelagic trawls, the individuals from demersal trawls are normally larger (and older) than those sampled pelagically. This has led to formation of a hypothesis saying that larger individuals tend to stay deeper than smaller individuals and some even to take up a demersal life. This hypothesis has not been tested, and during the winter surveys there are probably too few pelagic hauls to study the vertical distribution of capelin in a systematic way.

9.2 - Polar cod

Polar cod are not well represented in the trawl hauls conducted during the winter surveys (Figure 9.2). This is because this endemic arctic species has a more northern and eastern distribution area in the Barents Sea. During this time of the year, polar cod is known to be spawning under the ice-covered areas of the Pechora Sea and close to Novaya Zemlya. It is not clear whether the concentrations found in open water this time of the year are mature fish either on their way to spawning or from the spawning areas, or if this is immature fish. In 2022, catch rates of polar cod were high in the central Barents Sea close to/inside the ice possibly reflecting the increased abundance of this species in the last years.

 

CAPELIN. Distribution in the trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 9.1. CAPELIN. Distribution in the trawl catches winter 2022 ( number per nm 2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

 

POLAR COD. Distribution in the trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 9.2 POLAR COD. Distribution in the trawl catches winter 2022 ( number per nm 2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

9.3 - Blue whiting

Since the second part of the 1990s, blue whiting has shown a wider distribution than previously, and echo recordings have indicated higher abundance in the Barents Sea. Figure 9.3 shows the geographical distribution of the bottom trawl catch rates of blue whiting in 2022. Since the fish is mainly found pelagically, the bottom trawl does not reflect the real density distribution but gives some indication of the distribution limits. Acoustic observations would better reflect the relative density distribution. The number of pelagic hauls has, however, been too low to properly separate the pelagic recordings. During the years with high abundance of blue whiting, dense concentrations of blue whiting might have masked recordings of pelagic redfish, haddock and small cod.

Table 9.1 shows the bottom trawl swept area estimates by 5 cm length groups for the years 1994-2022. High abundance of fish below 20 cm in several years, e.g., 2001, 2004, 2012, 2015, and 2021 reflects abundant recruiting year-classes (age 1). The distribution of blue whiting in the Barents Sea reflects mostly abundance of younger age groups, i.e., when there are strong year-classes coming into the stock they are seen in the winter survey in the Barents Sea as 1-group the year after. The 2014 year-class is very strong, and this is reflected in the survey in 2015 as fish smaller than 20 cm. 2020 and 2021 year-classes are also regarded as strong.

Relatively high abundance of blue whiting was found in the extended survey area the last two years, similar to the situation with abundant recruiting year-classes (Tables 9.2). Table 9.3 presents estimates of coefficients of variation (%) by length groups. In most years, CVs for most length groups are above what could be considered as acceptable for stock assessment.

 

BLUE WHITING. Distribution in the trawl catches winter 2022 (number per nm2). Black crosses indicate zero catches and the stippled line the ice edge.
Figure 9.3 BLUE WHITING. Distribution in the trawl catches winter 2022 (number per nm 2 ). Black crosses indicate zero catches and the stippled line the ice edge.

 

  Length group (cm)   Biomass
Year 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40 Total (‘000 t)
1994 0 0 1.2 13.6 25.7 10.9 1.1 0.1 52.6 NA
1995 0 0.5 0.8 2.4 10.3 10.8 3.9 0.2 29.0 NA
1996 0 80.0 1371.8 8.4 18.6 7.1 3.8 0.1 1489.9 38.2
19971 0 608.7 681.5 273.8 3.1 5.3 1.8 0.1 1574.3 NA
19981 0 1.2 34.5 42.2 3.6 1.5 1.4 0.1 84.5 NA
1999 0 0.02 11.0 40.0 16.1 5.0 1.7 0.1 74.0 NA
2000 0 12.3 557.5 44.1 25.7 4.4 0.7 0.1 644.9 NA
2001 0.04 311.6 1420.8 631.5 46.0 5.4 1.6 0.1 2417.0 NA
2002 0 0.9 428.9 636.3 77.6 17.5 3.2 0.1 1164.4 56.6
2003 0 3.9 220.5 493.4 73.4 28.0 4.0 0.3 823.4 48.1
2004 0 7.1 712.0 821.6 276.2 37.8 1.1 0.2 1856.0 95.8
2005 0 125.1 717.2 984.7 223.3 31.8 0.1 0.1 2082.4 105.0
20062 0 0 164.4 1500.5 598.0 69.0 2.0 0.1 2333.9 172.9
20071 0 0 4.0 628.0 299.3 23.5 1.6 0.4 956.8 79.8
2008 0 0 0.3 12.1 126.1 19.8 1.3 0.1 159.7 20.6
2009 0 0 0.02 2.7 50.6 21.2 1.5 0.02 76.1 11.4
2010 0 0 0.5 1.6 9.4 16.9 1.0 0 29.4 5.2
2011 0 0 0.1 0.3 2.8 5.1 2.5 0 10.6 2.2
20121 0 85.6 674.6 1.1 1.8 5.3 2.0 0.3 770.7 18.2
2013 0 0 75.3 395.9 12.6 11.5 6.8 0.1 502.2 28.6
2014 0 0 182.1 34.2 9.7 1.6 1.5 0.04 229.2 8.5
2015 0 115.6 907.4 141.2 40.8 8.8 7.4 0 1221.3 34.2
2016 0 0.1 260.0 367.6 38.0 6.3 3.0 0.1 674.9 39.1
20171 0 0 29.1 939.6 279.2 26.1 11.5 0.05 1285.6 99.7
2018 0 0.02 0.8 45.4 50.2 8.3 1.7 0 106.5 10.5
2019 0.1 1.7 54.4 4.5 35.9 13.0 1.0 0.09 110.7 9.2
20201 0.2 14.3 154.9 25.4 7.9 8.1 0.6 0 212.8 11.5
20211 0 1.5 857.8 88.9 11.1 2.1 0.2 0 961.9 37.5
20221 0 13.3 311.0 260.6 11.6 3.5 1.3 0 601.4 25.9
Table 9.1. BLUE WHITING. Abundance indices (numbers in millions) from bottom trawl surveys in the Barents Sea standard area winter 1994-2022.

1 Indices not raised to represent the Russian EEZ or uncovered parts , blue whiting is mainly found in areas A, B, C and S

2 Not complete coverage in southeast due to restrictions, strata 7 area set to default and strata 13 as in 2005

  Length group (cm)   Biomass
Year 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40 Total (‘000 t)
2014 0 0 0.29 0.28 0.10 0.19 0.13 0 1.0 0.12
2015 0 0 0.16 0.10 0.25 0.78 0.42 0 1.7 0.27
2016 0 0 2.12 5.35 1.54 0.46 0.35 0 9.8 0.84
2017 0 0 0.08 20.91 4.10 1.34 0.39 0 26.8 1.98
2018 0 0 0 0.16 0.37 0.23 0.16 0 0.9 0.13
2019 0 0 0.03 0.21 0.71 0.70 0.24 0 1.9 0.34
2020 0 0 0.11 0.27 0 0.13 0 0 0.5 0.05
2021 0 0 9.60 3.53 0.48 0.41 0.07 0 14.1 0.63
2022 0 0 1.77 4.15 0.17 0.10 0 0 6.2 0.32
Table 9.2. BLUE WHITING. Abundance indices (numbers in millions) for new strata 24-26 from bottom trawl surveys in the Barents Sea winter 2014-2022.
  Length group (cm)
Year 5-9 10-14 15-19 20-24 25-29 30-34 35-39 40-44
1994 - - 94 68 51 28 31 49
1995 - 59 55 51 66 32 28 48
1996 - 49 79 56 49 30 33 59
19971 - 30 29 33 36 29 37 70
19981 - 91 60 33 35 33 28 70
1999 - 98 26 27 28 31 43 71
2000 - 37 21 20 25 29 31 95
2001 69 21 18 25 26 35 39 90
2002 - 56 25 17 20 33 52 69
2003 - 87 47 23 17 27 58 83
2004 - 86 23 19 15 14 30 61
2005 - 28 25 16 24 24 71 90
20062 - - 17 12 13 26 46 61
20071 - - 50 16 12 17 42 84
2008 - - 51 59 27 22 47 82
2009 - - 97 60 21 20 61 95
2010 - - 91 80 29 25 33 -
2011 - - 100 88 45 48 62 -
20122 - 32 30 39 45 38 29 98
2013 - - 70 31 57 44 44 99
2014 - - 23 23 24 27 18 137
2015 - 50 21 21 31 31 37 -
2016 - 96 33 24 17 27 29 97
20172 - - 24 16 16 16 42 101
2018 - 102 49 25 17 19 32 -
2019 68 37 38 29 35 31 50 101
20202 94 90 39 27 28 29 46 -
20212 - 48 23 30 32 24 45 -
20222 - 73 25 18 29 34 72 -
Table 9.3. BLUE WHITING. Estimates of coefficients of variation (%) for swept area abundance indices. Barents Sea standard area winter 1994-2022.

1 Russian EEZ not covered

2 Russian EEZ partly covered

10 - References

Aglen, A. and Nakken, O. 1997. Improving time series of abundance indices applying new knowledge. Fisheries Research, 30: 17-26.

Aglen, A., Dingsør, G., Mehl, S., Murashko, P. and Wenneck, T. de L. 2012. Results from the Joint IMR-PINRO Barents Sea demersal fish survey 21 January – 15 March 2012. WD #3 ICES Arctic Fisheries Working Group, Copenhagen, Denmark 20-26 April 2012.

Aschan, M. and Sunnanå, K. 1997. Evaluation of the Norwegian shrimp surveys conducted in the Barents Sea and Svalbard area 1980-1997. ICES C M 1997/Y:07. 24pp.

Dalen, J. and Nakken, O. 1983. On the application of the echo integration method. ICES CM 1983/B: 19, 30 pp.

Dalen, J. and Smedstad, O. 1979. Acoustic method for estimating absolute abundance of young cod and haddock in the Barents Sea. ICES CM 1979/G:51, 24pp.

Dalen, J. and Smedstad, O. 1983. Abundance estimation of demersal fish in the Barents Sea by an extended acoustic method. In Nakken, O. and S.C. Venema (eds.), Symposium on fisheries acoustics. Selected papers of the ICES/FAO Symposium on fisheries acoustics. Bergen, Norway, 21-24 June 1982. FAO Fish Rep., (300): 232-239.

Dickson, W. 1993a. Estimation of the capture efficiency of trawl gear. I: Development of a theoretical model. Fisheries Research 16: 239-253.

Dickson, W. 1993b. Estimation of the capture efficiency of trawl gear. II: Testing a theoretical model. Fisheries Research 16: 255-272.

Dolgov, A. V., Yaragina, N.A., Orlova, E.L., Bogstad, B., Johannesen, E., and Mehl, S. 2007. 20th anniversary of the PINRO-IMR cooperation in the investigations of feeding in the Barents Sea – results and perspectives. Pp. 44-78 in ‘Long-term bilateral Russian-Norwegian scientific cooperation as a basis for sustainable management of living marine resources in the Barents Sea.’ Proceedings of the 12th Norwegian- Russian symposium, Tromsø, 21-22 August 2007. IMR/PINRO report series 5/2007, 212 pp.

Engås, A. 1995. Trålmanual Campelen 1800. Versjon 1, 17. januar 1995, Havforskningsinstituttet, Bergen. 16 s. (upubl.).

Engås, A. and Godø, O.R. 1989. Escape of fish under the fishing line of a Norwegian sampling trawl and its influence on survey results. Journal du Conseil International pour l'Exploration de la Mer, 45: 269-276

Engås, A. and Ona, E. 1993. Experiences using the constraint technique on bottom trawl doors. ICES CM 1993/B:18, 10pp.

Fall, J. 2020. NEA cod and haddock indices from the Barents Sea winter survey 2020. Working Document # 10 Arctic Fisheries Working Group, ICES HQ (via webex), Copenhagen, Denmark, 16-22 April 2020

Foote, K.G. 1987. Fish target strengths for use in echo integrator surveys. Journal of the Acoustical Society of America, 82: 981-987.

Godø, O.R. and Sunnanå, K. 1992. Size selection during trawl sampling of cod and haddock and its effect on abundance indices at age. Fisheries Research, 13: 293-310.

ICES 2012. ICES. (Aglen, A., Bogstad, B., Dingsør, G.E., Gjøsæter, H., Hallfredsson, E.H., Mehl, S., Planque, B. et al.) 2012. Report of the Arctic Fisheries Working Group, ICES Headquarters, Copenhagen 20-26 April 2012. ICES CM 2012/ACOM: 05. 633 pp.

ICES 2020. Benchmark Workshop for Demersal Species (WKDEM). ICES Scientific Reports. 2:31. 136 pp. http://doi.org/10.17895/ices.pub.5548

ICES 2021. Benchmark Workshop for Barents Sea and Faroese Stocks (WKBARFAR). ICES Scientific Reports. 3:21. 2015 pp. https://doi.org/10.17895/ices.pub.7920

Jakobsen, T., Korsbrekke, K., Mehl, S. and Nakken, O. 1997. Norwegian combined acoustic and bottom trawl surveys for demersal fish in the Barents Sea during winter. ICES CM 1997/Y: 17, 26 pp.

Johannesen, E., Wenneck, T. de L., Høines, Å., Aglen, A., Mehl, S., Mjanger, H., Fotland, Å., Halland, T. I. and Jakobsen, T. 2009. Egner vintertoktet seg til overvåking av endringer i fiskesamfunnet i Barentshavet? En gjennomgang av metodikk og data fra 1981-2007. Fisken og Havet nr. 7/2009. 29s.

Johnsen, E., Totland, A., Skålevik, Å., Holmin, A. J., Dingsør, G. E., Fuglebakk, E., & Handegard, N. O. (2019). StoX: An open source software for marine survey analyses. Methods in Ecology and Evolution, 10(9), 1523-1528.

Jolly, G. M., & Hampton, I. (1990). A stratified random transect design for acoustic surveys of fish stocks. Canadian Journal of Fisheries and Aquatic Sciences, 47(7), 1282-1291.

Knudsen, H.P. 1990. The Bergen Echo Integrator: an introduction. - Journal du Conseil International pour l’Exploration de la Mer, 47: 167-174.

Korneliussen, R. J., Heggelund, Y., Macaulay, G. J., Patel, D., Johnsen, E., & Eliassen, I. K. (2016). Acoustic identification of marine species using a feature library. Methods in Oceanography, 17, 187-205.

Korsbrekke, K. 1996. Brukerveiledning for TOKT312 versjon 6.3. Intern program dokumentasjon., Havforskningsinstituttet, september 1996. 20s. (upubl.).

Korsbrekke, K., Mehl, S., Nakken, O. og Sunnanå, K. 1995. Bunnfiskundersøkelser i Barentshavet vinteren 1995. Fisken og Havet nr. 13 - 1995, Havforskningsinstituttet, 86 s.

MacLennan, D.N. and Simmonds, E.J. 1991. Fisheries Acoustics. Chapman Hall, London, England. 336pp.

Mehl, S., Aglen, A. and Johnsen, E. 2016. Re-estimation of swept area indices with CVs for main demersal fish species in the Barents Sea winter survey 1994-2016 applying the Sea2Data StoX software. Fisken og havet 10/2016. Institute of Marine Research, Bergen, Norway. 43 pp.

Mehl, S., Aglen, A., Johnsen, E. and Skålevik, Å. 2018. Estimation of acoustic indices with CVs for cod and haddock in the Barents Sea winter survey 1994 – 2017 applying the Sea2Data StoX software. Fisken og havet no. 5-2018. ISSN 0071-5638. Institute of Marine Research, Bergen, Norway. 29 pp.

Mehl, S. and Yaragina, N.A. 1992. Methods and results in the joint PINRO‑IMR stomach sampling program. Pp. 5-16 in Bogstad, B. and Tjelmeland, S. (eds.): Interrelations between fish populations in the Barents Sea. Proceedings of the fifth PINRO-IMR Symposium, Murmansk, 12-16 August 1991. Institute of Marine Research, Bergen, Norway.

Mjanger, H., Svendsen, B.V., Fuglebakk, E., Skage, M.L., Diaz, J, Johansen, G.O., Vollen, T, Bruck, S. A., and Gundersen, S. 2021. Handbook for sampling fish, crustaceans and other invertebrates. Version 16.00. October 2021. Ref.id.: FOU.SPD.HB-05, Institute of Marine Research. 146 pp.

Totland, A. and Godø, OR. 2001. BEAM – an interactive GIS application for acoustic abundance estimation.

In T. Nishida, P.R. Kailola and C.E. Hollingworth (eds.): Proceedings of the First Symposium on Geographic Information System (GIS) in Fisheries Science. Fishery GIS Research Group. Saitama, Japan.

11 - Appendix 1 . Survey design and methods for target species index calculation

Johan Hjort

Introduction

The Institute of Marine Research (IMR), Bergen, has performed acoustic measurements of demersal fish in the Barents Sea since 1976. Since 1981 a bottom trawl survey has been combined with the acoustic survey. Typical effort of the combined survey has been 10-14 vessel-weeks, and about 350 bottom trawl hauls have been made each year. After 2018, the Russian zone has been relatively well-covered and around 500 bottom trawl hauls have been made each year. Most years three vessels have participated from about February 1 to March 15.

The purpose of the investigations is presently:

  • Obtain acoustic abundance indices by length and age for cod and haddock

  • Obtain swept area abundance indices by age for cod and haddock

  • Obtain swept area abundance indices by length for redfish, Greenland halibut and blue whiting

  • Map the geographical distribution of those fish stocks

  • Estimate length, weight and maturity at age for cod and haddock

  • Collect stomach samples from cod, for estimating predation by cod

  • Map the distribution of maturing/pre-spawning capelin

Data and results from the survey are used both for stock assessments in the ICES Arctic Fisheries Working Group (AFWG) and by several research projects at IMR and PINRO, the Polar branch of the Russian Federal Research Institute of Fisheries and Oceanography (VNIRO).

From 1981 to 1992 the survey area was fixed (strata 1-12, main areas ABCD in Fig. 2.1). Due to warmer climate and increasing stock size in the early 1990s, the cod distribution area increased. Consequently, in 1993 and further in 1994 the survey area was extended to the north and east (strata 13-23, main areas D’ES in Fig. 2.1) to obtain a more complete coverage of the younger age groups of cod, and since then the survey has aimed at covering the whole cod distribution area in open water. For the same reason, the survey area was extended further northwards in the western part in 2014 (strata 24-26 in Fig. 2.1). In many years since 1997 Norwegian research vessels have had limited access to the Russian EEZ, and in 1997, 1998, 2007 and 2016 the vessels were not allowed to work in the Russian EEZ. In 1999 a rather unusually wide ice-extension partly limited the coverage. Since 2000, except in 2006, 2007 and 2017, Russian research vessels have participated in the survey and the coverage has been better, but for various reasons incomplete in most years. In 2008-2015 and 2018-2020 Norwegian vessels had access to major parts of the Russian EEZ. The coverage was more complete in these years, especially in 2008, 2011 and 2014. Table 3.5 summarizes degree of coverage and main reasons for incomplete coverage in the Barents Sea winter 1981-2021.

According to the joint IMR-PINRO long-term monitoring plan for the Barents Sea, developed during a series of meeting between the institutes, and agreed to be implemented at the annual meeting between Russian and Norwegian scientists in Tromsø, 13-15 March 2018, the winter survey is from 2019 a joint IMR-PINRO survey with commitments from both institutes jointly to seek obtaining a total coverage of the main demersal fish resources in the area.

Methods

Swept area measurements

All vessels were equipped with the standard research bottom trawl Campelen 1800 shrimp trawl with 80 mm (stretched) mesh size in the front. Prior to 1994 a cod-end with 35-40 mm (stretched) mesh size and a cover net with 70 mm mesh size were mostly used. Since this mesh size may lead to considerable escapement of 1-year-old cod, the cod-ends were in 1994 replaced by cod-ends with 22 mm mesh size. At present a cover net with 116 mm meshes is mostly used.

The trawl is now equipped with a rockhopper ground gear (Engås and Godø 1989). Until and including 1988 a bobbins gear was used, and the cod and haddock indices from the period 1981-1988 have since been recalculated to ‘rockhopper indices’ and adjusted for length dependent catch efficiency and/or sweep width (Godø and Sunnanå 1992, Aglen and Nakken 1997). The sweep wire length is 40 m, plus 12 m wire for connection to the doors.

In the Norwegian Barents Sea shrimp survey (Aschan and Sunnanå 1997) the Campelen trawl has been rigged with some extra floats (45 along the ground rope and 18 along the under belly and trunk, all with 20mm diameter) to reduce problems on very soft bottom. This rigging has been referred to as “Tromsø rigging”. When the shrimp survey was terminated 2004 and later merged with the Barents Sea Ecosystem survey in 2005, improved shrimp data were also requested from the winter survey, and the “Tromsø rigging” was used in parts of the shrimp areas in 2004 (11 stations) and 2005 (9 stations). In 2006-2014 “Tromsø rigging” was used for nearly all bottom trawl stations taken by Norwegian vessels in the winter survey, while since 2015 “Tromsø rigging” has not been applied.

Vaco doors (6 m2, 1500kg), were previously standard trawl doors on board the Norwegian research vessels. On the Russian vessels and hired vessels V-type doors (ca 7 m2) have been used. In 2019 the Russian vessel used 5 m2 “Sparrow” trawl doors weighing 2000 kg. In 2004, R/V “Johan Hjort” and R/V “G.O. Sars” started using a V-type door for bottom trawling (Steinshamn W-9, 7.1m2 , 2050 kg), the same type as used on the Russian research vessels. In 2010 the V-doors were replaced by 125” Thyborøn trawl doors. R/V “Helmer Hanssen” has used Thyborøn trawl doors since the 2008 survey. To achieve constant sampling width of a trawl haul independent of e.g. depth and wire length, a 10-15 m rope “locks” the distance between the trawl wires 80-150 m in front of the trawl doors on the Norwegian vessels. This is called “strapping”. The distance between the trawl doors is then in most hauls restricted to the range 48-52 m regardless of depth (Engås and Ona 1993, Engås 1995). Strapping was first attempted in the 1993 survey on board one vessel, in 1994 it was used on every third haul and in 1995-1997 on every second haul on all vessels. Since 1998 it has been used on all hauls when weather conditions permitted. Strapping is not applied on the Russians vessels, but the normal distance between the doors is about 50 m (D. Prozorkevich, pers. comm.).

Standard tow duration is now 15 minutes (until 1985 the tow duration was 60 min. and from 1986 to 2010 30 min.). Trawl performance is constantly monitored by Scanmar trawl sensors, i.e., distance between the doors, vertical opening of the trawl and bottom contact control. In 2005-2008 sensors monitoring the roll and pitch angle of the doors were used due to problems with the Steinshamn W-9 doors. The data is logged on files but have so far not been used for further evaluation of the quality of the trawl hauls.

At the start of the survey at least two of the trawls on the Norwegian vessels should go through a “sea test”. The purpose of the test is to check that the geometry of the trawl is within the specified limits and that the trawl performance is satisfactory, especially that the bottom contact is stable. It is further checked that the trawl sensors operate as they should.

The positions of the trawl stations are pre-defined. When the swept area investigations started in 1981 the survey area was divided into four main areas (A, B, C and D, Fig 2.1) and 35 strata.

 

Strata (1-23) and main areas (A,B,C,D,D’,E and S) used for swept area estimations and acoustic estimations with StoX. Additional strata (24-26, main area N) are covered since 2014, and are from 2020 included in the standard time series for haddock and from 2021 in the time series for cod.
Figure 2.1. Strata (1-23) and main areas (A,B,C,D,D’,E and S) used for swept area estimations and acoustic estimations with StoX. Additional strata (24-26, main area N) are covered since 2014, and are from 2020 included in the standard time series for haddock and from 2021 in the time series for cod.

 

During the first years, the number of trawl stations in each stratum was set based on expected fish distribution to reduce the variance, i.e., more hauls in strata where high and variable fish densities were expected to occur. During the 1990s trawl stations were spread out more evenly, yet the distance between stations in the most important cod strata is shorter (16 or 20 NM) compared to the less important strata (24, 30 or 32 NM). Considerable amounts of young cod were now distributed outside the initial four main areas, and in 1993 the investigated area was therefore enlarged by areas D’, E, and the ice-free part of Svalbard (S) (Fig. 2.1 and Table 1.4 in main report), 28 strata altogether. In the 1993-1995 survey reports, the Svalbard area was included in area A’ and the western part of area E (west of 30 ° E). Since 1996 a revised strata system with 23 strata has been used (Figure 2.1). The main reason for reducing the number of strata was the need for enough trawl stations in each stratum to get reliable estimates of density and variance. In 2014 the investigated area was enlarged by three new strata in northwest, 24-26 (main area N, Fig. 2.1). From 2020, these strata were included in the swept area and acoustic indices for haddock and from 2021, they were included for cod (see next section). They are not yet included in the standard time series for the other species.

Sampling of catch and age-length keys

Sorting, weighing, measuring and sampling of the catch are done according to instructions given in Mjanger et al . (2021). Since 1999 all data except age are recorded electronically by Scantrol Fishmeter measuring board, connected to stabilized scales. The whole catch or a representative sub sample of most species was length measured on each station.

At each trawl station, one cod and haddock per 5 cm length-group is sampled for age (otoliths), individual weights, sex, and maturity. For cod, stomach samples are also taken from the same individuals. For the largest cod, other sampling schemes have been used in some years; in 2007-2009, all cod above 80 cm were sampled, and in 2010 all above 90 cm were sampled, limited to 10 per station. The stomach samples from cod are frozen and analysed after the survey. Greenland halibut otoliths are also sampled from one specimen per 5 cm length-group, while otoliths from the redfish species Sebastes norvegicus and S. mentella are sampled from two fish in every 5-cm length-group on every station. Table 2.1 in the annual report gives an account of the sampled material, and further details on the sampling protocol can be found in the sampling manual for the Winter survey (updated annually).

Swept area fish density estimation

Swept area fish density estimates ( r k,l,s ) for each station s in stratum k are first estimated by length ( l ) for each bottom trawl haul by the equation:

Formel

Formel number of fish of length l per n.m.2 observed on trawl station s in stratum k

Formel estimated frequency of length l

Formel swept area:

Formel

Formel towed distance (nm)

Formel length dependent effective fishing width. The fishing width was previously fixed to 25 m = 0.0135 nm. Based on Dickson (1993a,b, Table 1), length dependent effective fishing width was included in the calculations for cod and haddock from 1995 (Korsbrekke et al ., 1995) as such:

Formel for Formel

Formel = Formel for Formel

Formel = Formel for Formel

Species l min l max
Cod 5.91 0.43 15 cm 62 cm
Haddock 2.08 0.75 15 cm 48 cm
Table 1 : Species-specific parameters from Dickson (1993a, b) used to calculate length-dependent effective fishing width for cod and haddock.

For redfish, Greenland halibut and other species, a fishing width of 25 m is applied, independent of fish length.

After applying the length-dependent effective fishing width, the station-specific length distributions (swept area density by length) are aggregated into 5 cm length groups.

Next, the abundance (N individuals) by 5 cm length group l and stratum k are calculated as:

Formel

Where A is the area (nmi2) of stratum k and ρk,l is the average swept area density by l in the stratum, given by:

Formel

Where n is the number of stations in the stratum.

A two-stage conversion process is used to convert the abundance of fish by length group to abundance of fish by age group. First, the abundance (Nk,l ) by length group and stratum is distributed the length-measured individuals (j) to generate so-called “Super-individuals” (super-individuals represent fractions of a total; our use corresponds to a probability based design where Formel is the inverse of the inclusion probability for a single fish sample), each representing an abundance estimated as:

Formel

Where,

Formel

and m is the number of length-measured individuals.

Second, in instances where a super-individual is not aged, the missing age is filled in by a random data imputation. The imputation of missing age is first carried out at the station level, randomly selecting the value from aged super-individuals within the same length group. If no aged super-individual is available at the station level, the imputation is attempted at strata level, or lastly at survey level. In instances where no age information is available at any level for a specific length group, the abundance estimate is presented with unknown age (Johnsen et al., 2019).

Acoustic measurements

The method is explained by Dalen and Smedstad (1979, 1983), Dalen and Nakken (1983), MacLennan and Simmonds (1991) and Jakobsen et al. (1997). The acoustic equipment has been continuously improved. Since the early 1990s Simrad EK500 echo sounder and Bergen Echo Integrator (BEI, Knudsen 1990) were used. The Simrad EK60 echo sounder replaced the EK500 on R/V “Johan Hjort” in 2005 and on R/V “Helmer Hanssen” since the 2008 survey. The latest R/V “G.O. Sars” has used EK60 since it replaced R/V “Sarsen” (former R/V “G.O. Sars”) in 2004. The Large Scale Survey System (LSSS, Korneliussen et al . 2016) replaced BEI on R/V “G.O. Sars” and R/V “Johan Hjort” in 2007 and on R/V “Helmer Hanssen” since the 2008 survey. On the Russian vessels EK 500 was used from 2000 to 2004 and ER60 since 2005. In 2021 the Russian vessel used EK60 with software ER60 v 2.2.1, and LSSS v. 1.9.0 The new Simrad EK80 echo sounder has been used on R/V “G.O. Sars” since 2017 and on R/V “Johan Hjort” since 2018. In 2021 LSSS v. 2.10.0 was used on “Johan Hjort”, while version 2.9.0 was used on “Helmer Hanssen” and “Kronprins Haakon”.

In the mid-1990s the echo sounder transducers were moved from the hull to a retractable centreboard, on R/V “Johan Hjort” since the 1994 survey, on R/V “Sarsen” (former R/V “G.O. Sars”) since 1997, on the latest R/V “G.O. Sars in 2004 and on R/V “Helmer Hanssen” since the 2008 survey. This latter change has largely reduced the signal loss due to air bubbles in the close to surface layer. None of the Russian vessels have retractable centreboards.

On both Norwegian and Russian vessels, acoustic backscattering values (sA = nautical area scattering coefficient NASC) are stored at high resolution in LSSS. After scrutinizing and allocating the values to species or species groups, the values are stored with 10 m vertical resolution and 1 nautical mile (NM) horizontal resolution. The procedure for allocation by species is based on:

  • composition in trawl catches (pelagic and demersal hauls)

  • the appearance of the echo recordings

  • inspection of target strength distributions

  • inspection of target frequency responses

For each trawl catch the relative sA-contribution from each species is calculated (Korsbrekke 1996) and used as a guideline for the allocation. In these calculations, the fish length dependent catching efficiency of cod and haddock in the bottom trawl (Aglen and Nakken 1997) is taken into account. There is no reason to believe that trawl catches give an accurate representation of species composition in the sea, so the calculated sA -contribution from the trawl hauls are used as a guidance only.

Acoustic fish density estimation

The new Sea2Data software StoX has been applied to estimate acoustic indices with CVs for cod and haddock. Acoustic estimates for the period 1994-2017 were re-estimated using StoX (Mehl et al. 2018). The main difference between the SAS based BEAM Program (Totland and Godø 2001) used until 2017 and StoX acoustic abundance estimation is that in BEAM the survey area is divided into rectangles, and for each rectangle an average acoustic density (sA ) is calculated, while in StoX transects are defined within each stratum (Figure 2.1) as primary sampling units (PSUs) and used to calculate acoustic density (Jolly and Hampton 1990).

Within each stratum, the acoustic course tracks are divided into transects, separated by the trawl stations in the stratum since the course tracks run through the net of fixed bottom trawl stations in the bottom trawl survey. A distance of about 2 nautical miles around each station is not included in the transects. For the time series 1994-2017 this was done by first running a R-script tagging all the transects and then the transects were inspected and edited manually in StoX if necessary. Minimum length of a transect was set to 4 nautical miles. In this process miles with obvious errors in the sA -values, e.g. bottom contribution, were removed from the transects. From 2018, all transects have been defined manually using the built-in functionality in the StoX software following the same rules as described above.

For each transect and stratum, an arithmetic mean sA is calculated for the water column. The conversion of mean NASC (m2 nmi−2 ) to density of fish follows a standard procedure where all trawl stations within a stratum with a catch of more than 5 individuals are assigned to each PSU. If less than 3 trawl stations had been carried out in a stratum, stations in neighbouring strata is assigned to the PSUs such that at least 3 stations are assigned to each PSU. From 2021, the criterion of having minimum 5 individuals in the catch was excluded as this type of filtration is not implemented in the new StoX version.

The combined length distribution ( d ) is calculated for each transect (PSU ( j )) as:

Formel

where dl,s,j is density (number by 1 NM tow distance) by 1 cm length group ( l ) for the stations ( s ) assigned to PSU ( j ).

The trawl catches are normalised to 1 NM towing distance and adjusted for length dependent catch efficiency as describe for swept area estimation above.

The areal density of fish (ρ) (n per nmi2 ) by length group l by transect j is calculated as

Formel

where NASCj,l is the mean nautical area scattering coefficient by transect (j) and length group (l) and σl is the acoustic backscattering cross-section for a fish of length l .

NASCj,l is calculated as:

Formel

where σl,p is the acoustic backscattering cross-section for a fish of length l multiplied with the proportion (p) of a fish of length l in the total length distribution and NASCj is the mean nautical area scattering coefficient in transect j .

The acoustic backscattering cross-section (m2 ) for a fish of length l is calculated as

Formel

where the target strength, TS , for a fish of length l (cm) is calculated as

Formel

Where m and a are constants. For cod and haddock, we apply:

Formel  (Foote, 1987) 

The fish abundance ( N ) by length group ( l ) for stratum k is then:

Formel ,

where A is stratum area and the mean density of fish of length group l and stratum k is:

Formel

where Formel (j= 1,2, nk) are the lengths of the nk sample transects.

Estimates by length are converted to estimates by age using the same age imputation method described for the swept area index estimation. The abundance by stratum is then summed for defined main areas (Figure 2.1).

Software for index estimation

The Sea2Data software StoX (Johnsen et al. 2019) has been applied to estimate swept area indices with CVs for cod, haddock, golden redfish, beaked redfish, Norway redfish, Greenland halibut and blue whiting. Swept area estimates for the period 1994-2016 was re-estimated using StoX (Mehl et al . 2016). The entire haddock time series was revised again in 2020 using StoX, in connection with the ICES Benchmark Workshop for Demersal Species (ICES 2020). This involved including strata 24-26 in the official time series from 2014, the use of bootstrap mean instead of baseline estimates for abundance at age, and standardising the length groups used in the length-dependent sweep width function (Fall 2020). The additional strata were also included in the acoustic index for haddock, while the other changes were made to the swept area index only. In 2021, the same changes were made to the cod time series (ICES 2021). The revised swept area index for haddock was produced with R version 3.5.3 (years 1994-2013) and R version 3.6.2 (years 2014-2019). In the update of R to 3.6.X, the random seed generator was changed, which means that the same seed will give slightly different results compared to 3.5.X. This results in minor differences to the bootstrapped estimates if old StoX projects are run with the new R version. In 2019 and 2020 StoX version 2.7 and RStoX 1.11 were used to produce indices. The same version was used for blue whiting, Greenland halibut and redfish in 2021, while StoX version 3.3.0 was used for cod and haddock.

The main difference between the SAS based Survey Program previously used (years 1981-1993 of the time-series, see earlier survey reports for results and method details) and StoX swept area estimation is in the use of the age-length data. StoX does not use age-length keys (ALK) in the traditional sense with ALKs estimated for large areas. Missing age information is imputed from known age-length data within station, strata, or the entire survey (see below). StoX also allows for uncertainty estimation by bootstrapping primary sampling units (PSUs).

StoX input, filters and settings for cod and haddock

Input data for survey index estimation were downloaded from DatasetExplorer: https://datasetexplorer.hi.no/apps/datasetexplorer/v2/navigation . See section 3 in main report for information on what snapshot files were used in the current year.

The different functions and settings used in swept area estimation for cod and haddock in StoX 3.3.0 are detailed in Table 2. The functions are divided into the three parts of the StoX estimation process: baseline, analysis, and report.

Function Settings Purpose
Baseline    
ReadBiotic FileNames: paths to xml-files in biotic folder Reads in versioned biotic files.
StoxBiotic - Converts and trims data (only keeps key variables, standardises variable names etc.) to a common format used in StoX.
AddToStoxBiotic StoxBioticData: StoxBiotic BioticData: ReadBiotic VariableNames: gearcondition, samplequality, stationtype, length, maturationstage, otolithtype Add variables required for filtering or that are needed in output data.
FilterStoxBiotic (1) StoxBioticData: AddToStoxBiotic FilterExpression: {"Haul": "Gear %in% c(\"3270\", \"3271\") & gearcondition %in% c(\"1\", \"2\") & samplequality %in% c(\"1\", \"3\")"} FilterUpwards: true Data filtering; removes extra hauls taken on acoustic registrations and unsuccessful hauls, selecting data from bottom trawl only. See https://kvalitet.hi.no/docs/pub/DOK06839.pdf for explanation of the different codes used in the data.
FilterStoxBiotic (2) StoxBioticData: FilterStoxBiotic (1) FilterExpression: {"SpeciesCategory": "SpeciesCategory %in% \"torsk/164712/126436/Gadus morhua\""} FilterUpwards: false Data filtering; selecting data for the target species. For haddock, the SpeciesCategory is: "hyse/164744/126437/Melanogrammus aeglefinus\"
DefineStratumPolygon DefinitionMethod: ResourceFile FileName: input/ vintertokt_barentshavny.txt The resource file contains polygon definitions for the strata used in the Winter survey.
StratumArea StratumPolygon: DefineStratumPolygon AreaMethod: Accurate Calculates the area of each stratum.
LengthDistribution StoxBioticData: FilterStoxBiotic (2) LengthDistributionType: Normalized RaisingFactorPriority: Weight Calculates length frequency distributions for each station and haul. ‘Normalized’ refers to a length distribution that is standardised to one nautical mile towing distance (i.e., weighted by CPUE). The RaisingFactorPriority relates to how weighting is handled when the haul contains different subsamples for the same species. See StoX documentation for more details on length distributions.
RegroupLengthDistribution (1) LengthDistributionData: LengthDistribution LengthInterval: 1 Sets the length distribution resolution to 1 cm, i.e., 1 cm length groups. There may be length distributions with finer resolution, this will standardise it.
LengthDependentCatch-Compensation LengthDistributionData: RegroupLengthDistribution (1) CompensationMethod: LengthDependentSweepWidth LengthDependentSweepWidth- Parameters: [{"SpeciesCategory": "torsk/164712/126436/Gadus morhua","Alpha":5.91, "Beta":0.43, "LMin":15,"LMax":62}] Adjusts the length distributions for increasing catchability with length (based on the Dixon experiments). For haddock, the parameters are: [{"SpeciesCategory": "hyse/164744/126437/Melanogrammus aeglefinus","Alpha": 2.08, "Beta": 0.75, "LMin": 15, "LMax": 48}
RegroupLengthDistribution (2) LengthDistributionData: LengthDependentCatch- Compensation LengthInterval: 5 Regroups the length distribution to the same resolution as the age sample stratification: 5 cm length groups.
MeanLengthDistribution LengthDistributionData: RegroupLengthDistribution (2) StratumPolygon: DefineStratumPolygon LayerDefinition: FunctionParameter LayerDefinitionMethod: WaterColumn SurveyDefinition: FunctionParameter SurveyDefinitionMethod: AllStrata PSUDefinition: FunctionParameter PSUDefinitionMethod: StationToPSU Calculates the mean length distribution for each PSU by summing vertically and averaging horizontally. This allows mean length distributions to be calculated across e.g., hauls taken at the same PSU (station) but different depths. For the cod and haddock projects there is only one haul per PSU, which means that the purpose of this function is to define PSUs and convert the LengthDistribution object to a MeanLengthDistribution object for use in further calculations.
SweptAreaDensity MeanLengthDistributionData: MeanLengthDistribution SweptAreaDensityMethod: LengthDistributed SweepWidthMethod: PreDefined DensityType: "AreaNumberDensity" Calculates the area density of fish (number of individuals per square nautical mile). The sweep width method is set to pre-defined since this is already taken care of by the LengthDependentCatchCompensation process.
MeanDensity DensityData: SweptAreaDensity Calculates the average swept area density in each stratum. The average is weighted by the number of hauls per PSU, meaning that for a standard swept area project with one haul per PSU, this will be an unweighted average. For acoustic projects, the mean acoustic density is weighted by the effective log distance.
Abundance MeanDensityData: MeanDensity StratumAreaData: StratumArea Calculates the total abundance of each length group (also species category and layer when relevant) in each stratum based on the mean swept area density and stratum area.
Individuals StoxBioticData: FilterStoXBiotic (2) MeanLengthDistributionData: MeanLengthDistribution AbundanceType: SweptArea Defines the individual data that will be used to distribute the abundance on super individuals.
SuperIndividuals IndividualsData: Individuals AbundanceData: Abundance LengthDistributionData: RegroupLengthDistribution (2) DistributionMethod: HaulDensity Distributes abundance on the individuals, turning them into “Superindividuals”, each representing a part of the total abundance. Abundance can be divided equally on all individuals, or it can be divided proportionally to den density of the individual’s length group in the haul in which it was caught. Needed to get indices by age and to weigh biological parameters by abundance.
ImputeSuperIndividuals SuperIndividualsData: SuperIndividuals ImputationMethod: RandomSampling ImputeAtMissing: [“IndividualAge”] ImputeByEqual: ["Survey", "SpeciesCategory", "IndividualTotalLength"] ToImpute: ["IndividualAge", "maturationstage", "IndividualRoundWeight", "otolithtype"] Seed: 1 Identifies individuals that have missing data for a specified variable (here: age, as specified in “ImputeAtMissing”), and assigns the missing variables (and possibly others specified in “ToImpute”) by random sampling from other individuals in the same length group. First, the function looks for suitable individuals from the same haul. If there are none, the random draw extends to other hauls in the stratum, and lastly to the entire survey. Will return NA if no other individuals in the same length group have been aged in the survey. This has the advantage over a traditional age-length key in that it allows imputation of other variables than age.
Analysis    
Bootstrap BootstrapMethodTable: [{"ResampleFunction": "ResampleMeanLength-DistributionData", "ProcessName": "MeanLengthDistribution", "Seed":1}] NumberOfBootstraps: 500 OutputProcesses: ["ImputeSuperIndividuals", "SuperIndividuals"] UseOutputData: FALSE (not ticked) NumberOfCores: 6 BaselineSeedTable: [{"ProcessName": "ImputeSuperIndividuals", "Seed":1}] This function runs a subset of the baseline model several times (as specified in “NumberOfBootstraps”) after resampling trawl hauls in each stratum (with replacement). Here, the baseline model is rerun from MeanLengthDistribution to ImputeSuperIndividuals, calculating new length distributions based on the resampled trawl hauls and redoing the age imputation. The “UseOutputData” option can be used if, e.g., new reports are to be generated from a bootstrap object that has already been run – this option reads in the bootstrap object rather than running it again. The number of cores can be set higher if relevant (will use max number of cores if less than 6).
Report    
ReportBootstrap BootstrapData: Bootstrap BaselineProcess: ImputeSuperIndividuals TargetVariable: Abundance AggregationFunction: sum BootstrapReportFunction: summaryStox GroupingVariables: ["Survey", "SpeciesCategory", "IndividualAge"] RemoveMissingValues: FALSE Report bootstrap abundance. This function gives the 5 %, 50 % and 95 % quantiles and mean, sd and CV of abundance by age. The bootstrap mean abundance is used as the official estimate of swept area abundance for cod and haddock.
ReportBootstrap BootstrapData: Bootstrap BaselineProcess: ImputeSuperIndividuals TargetVariable: Biomass AggregationFunction: sum BootstrapReportFunction: summaryStox GroupingVariables: ["Survey", "SpeciesCategory", "IndividualAge"] RemoveMissingValues: FALSE Report bootstrap biomass.
ReportBootstrap BootstrapData: Bootstrap BaselineProcess: ImputeSuperIndividuals TargetVariable: Abundance AggregationFunction: sum BootstrapReportFunction: summaryStox GroupingVariables: ["Survey","SpeciesCategory, "Stratum", "IndividualAge"] RemoveMissingValues: FALSE Report bootstrap abundance by stratum and age.
ReportBootstrap BootstrapData: Bootstrap BaselineProcess: ImputeSuperIndividuals TargetVariable: Biomass AggregationFunction: sum BootstrapReportFunction: summaryStox GroupingVariables: ["Survey","SpeciesCategory", "Stratum", "IndividualAge"] RemoveMissingValues: FALSE Report bootstrap biomass by stratum and age.
ReportBootstrap BootstrapData: Bootstrap BaselineProcess: ImputeSuperIndividuals TargetVariable: length AggregationFunction: weighted.mean BootstrapReportFunction: summaryStox GroupingVariables: ["Survey","SpeciesCategory", "IndividualAge"] RemoveMissingValues: TRUE AggregationWeightingVariable: Abundance Report bootstrap mean length at age. The mean lengths are weighted by superindividual abundance at age (i.e., individuals from abundant length groups get higher weight).
  BootstrapData: Bootstrap BaselineProcess: ImputeSuperIndividuals TargetVariable: IndividualRoundWeight AggregationFunction: weighted.mean BootstrapReportFunction: summaryStox GroupingVariables: ["Survey","SpeciesCategory", "IndividualAge"] RemoveMissingValues: TRUE AggregationWeightingVariable: Abundance Report bootstrap mean weight at age. The mean weights are weighted by superindividual abundance at age (i.e., individuals from abundant length groups get higher weight).
Table 2 : StoX functions and settings used in the cod and haddock swept area estimations, split on the three parts of the StoX estimation process; baseline, analysis, and report.

*Note that this is the function name, not the process name – the latter can be freely decided by the user. If a function is used more than once, unique processes names must be given and care must be taken to refer to the right process in subsequent steps of the estimation process (as indicated by numbers after the function name).

Table 3 details the functions and settings used for cod and haddock acoustic estimation in StoX.

Function Settings Details
Baseline    
ReadAcoustic FileNames: paths to xml-files in acoustic folder Reads in versioned acoustic files.
StoxAcoustic - Converts and trims data (only keeps key variables, standardises variable names etc.) to a common format used in StoX.
FilterStoxAcoustic (1) StoxAcousticData: StoxAcoustic FilterExpression: {"Beam":"Frequency %in% 38000","ChannelReference": "ChannelReferenceType %in% \"P\""} FilterUpwards: FALSE Select data from 38 kHz only (in case data is stored on multiple frequencies) and select only pelagic channel data (contains data from entire water column).
FilterStoxAcoustic (2) StoxAcousticData: FilterStoxAcoustic(1) FilterExpression: {"AcousticCategory": "AcousticCategory %in% \"31\""} FilterUpwards: FALSE For haddock: "AcousticCategory %in% \"30\""
DefineTranslationBeam DefinitionMethod: TranslationTable TranslationTable: [{"VariableName":"Beam", "Value":"38000/1", "NewValue":"38000/2"}] Conditional: FALSE In some cases, the beam names are different on Norwegian and Russian vessels. This defines a key that connects the two names and is used to make sure all data from 38 kHz are included.
TranslateStox- AcousticBeam StoxAcousticData: FilterStoxAcoustic(2) Translation: DefineTranslationBeam Apply the translation to the acoustic data.
ReadBiotic FileNames: paths to xml-files in biotic folder As above.
StoxBiotic - As above.
AddToStoxBiotic StoxBioticData: StoxBiotic BioticData: ReadBiotic VariableNames: ["stationtype"]  
FilterStoxBiotic (1) StoxBioticData: AddToStoxBiotic FilterExpression: {"Station":"stationtype %notin% \"2\""} FilterUpwards: TRUE  
FilterStoxBiotic (2) StoxBioticData: FilterStoxBiotic(1) FilterExpression: {"SpeciesCategory": "SpeciesCategory %in% \"torsk/164712/126436/Gadus morhua\""} FilterUpwards: TRUE  
LengthDistribution StoxBioticData: FilterStoxBiotic(2) LengthDistributionType: Normalized RaisingFactorPriority: Weight  
RegroupLength- Distribution LengthDistributionData: LengthDistribution LengthInterval: 1  
LengthDependentCatch- Compensation LengthDistributionData: RegroupLengthDistribution CompensationMethod: LengthDependentSweepWidth LengthDependentSweep-WidthParameters: [{"SpeciesCategory": "torsk/164712/126436/Gadus morhua","Alpha":5.91, "Beta":0.43, "LMin":15,"LMax":62}] For haddock, the parameters are: [{"SpeciesCategory": "hyse/164744/126437/-Melanogrammus aeglefinus", "Alpha": 2.08, "Beta": 0.75, "LMin": 15, "LMax": 48}
RelativeLength- Distribution LengthDistributionData: LengthDependentCatch-Compensation Converts the length distribution to a relative one (in %).
DefineStratumPolygon   As above
StratumArea   As above
DefineAcousticPSU StoxAcousticData: TranslateStoxAcousticBeam DefinitionMethod: “Manual” Set to manual to define the transects by clicking in the GUI. After doing this once, the transect definitions are stored in the process data.
NASC StoxAcousticData: TranslateStoxAcousticBeam Converts the acoustic data to NASC data format.
MeanNASC NASCData: NASC AcousticPSU: DefineAcousticPSU LayerDefinition: FunctionParameter LayerDefinitionMethod: WaterColumn SurveyDefinition: FunctionParameter SurveyDefinitionMethod: AllStrata PSUDefinition: FunctionInput” Sums the NASC data vertically. Here: throughout the entire water column.
BioStationAssignment StoxBioticData: FilterStoxBiotic(2) StratumPolygon: DefineStratumPolygon AcousticPSU: DefineAcousticPSU StoxACousticData: TranslateStoxAcousticBeam DefinitionMethod: Stratum LayerDefinition: FunctionParameter LayerDefinitionMethod: WaterColumn Assigns trawl stations to each acoustic PSU; all trawl stations within the same strata as the acoustic PSU will be assigned to that PSU. In the case of few trawl stations in a strata, additional trawls from neighbouring strata can be added manually in the map window.
BioStationWeighting BioticAssignment: BioStationAssignment LengthDistributionData: RegroupLengthDistribution WeightingMethod: SumWeightedCount How to weight the trawl stations when calculating length distributions for each PSU. The “SumWeightedCount” option give weighting values that are proportional to the normalized length distribution count (i.e., cpue) in the haul.
AssignmentLength- Distribution LengthDistributionData: RelativeLengthDistribution BioticAssignment: BioStationAssignment Calculates weighted average length distributions for each PSU (and layer).
DefineAcousticTarget- Strength DefinitionMethod: TargetStrengthTable TargetStrengthMethod: LengthDependent TargetStrengthTable: [ {"AcousticCategory":"31", "Frequency": 38000, "TargetStrength0": -68, "LengthExponent": 20}] Specifies the target strength-length relation for the target species. The same settings are used for cod and haddock, except that the AcousticCategory is set to “30”.
AcousticDensity MeanNASCData: MeanNASC AssignmentLength-DistributionData: AssignmentLength-Distribution AcousticTargetStrength: DefineAcousticTarget- Strength SpeciesLink: [{"AcousticCategory":"31", "SpeciesCategory": "torsk/164712/126436/Gadus morhua"}] Calculate number density based on the acoustic target strength-length relationship. For haddock: SpeciesLink: [{"AcousticCategory": "30","SpeciesCategory": "hyse/164744/126437/-Melanogrammus aeglefinus"}]
MeanDensity DensityData: AcousticDensity Calculates the weighted average density in each stratum. The weights are the effective log distance of each acoustic PSU.
Abundance MeanDensityData: MeanDensity StratumAreaData: StratumArea Calculates abundance as the product of mean density and area of the stratum.
Individuals StoxBioticData: FilterStoxBiotic(2) BioticAssignment: BioStationWeighting AbundanceType: Acoustic As above.
SuperIndividuals IndividualsData: Individuals AbundanceData: Abundance LengthDistributionData: LengthDependentCatch-Compensation DistributionMethod: HaulDensity As above. Currently, the length distribution data is not regrouped to 5 cm length bins in the acoustic projects. This should be considered in the next revision.
ImputeSuperIndividuals SuperIndividualsData: SuperIndividuals ImputationMethod: RandomSampling ImputeAtMissing: ["IndividualAge"] ImputeByEqual: ["Survey","SpeciesCategory", "IndividualTotalLength"] ToImpute: ["IndividualRoundWeight", "LengthResolution", "WeightMeasurement", "IndividualSex", "IndividualAge"] Seed: 1 As above.
Analysis    
Bootstrap BootstrapMethodTable: [{"ResampleFunction": "ResampleMeanNASCData", "ProcessName": "MeanNASC", "Seed":1}, {"ResampleFunction": "ResampleBioticAssignment", "ProcessName": "BioStationWeighting", "Seed":2}] NumberOfBootstraps: 500 OutputProcesses: ["SuperIndividuals", "ImputeSuperIndividuals"] UseOutputData: FALSE NumberOfCores: 6 BaselineSeedTable: [{"ProcessName": "ImputeSuperIndividuals", "Seed":1}] As above.
Table 3 : StoX functions and settings used in the cod and haddock acoustic estimations, split on the three parts of the StoX estimation process; baseline, analysis, and report. For details on functions used also in the swept area index, refer to table 2.

For cod and haddock swept area and cod acoustic indices, the bootstrap mean estimate is used as the official index in stock assessment, while the haddock acoustic index is based on the baseline run (ICES 2020, 2021). To get baseline numbers, a report is generated based on SuperIndividualsData from the baseline run according to Table 4.

Report    
ReportSuperIndividuals SuperIndividualsData: ImputeSuperIndividuals TargetVariable: Abundance ReportFunction: sum GroupingVariables: ["Survey", "SpeciesCategory", "IndividualAge"] RemoveMissingValues: FALSE Report on variables from the superindividuals data, such as abundance at age or mean weight at age. This is based on the single baseline run rather than the 500 bootstrap iterations.
Table 4 : Function used to generate a baseline abundance report.

Estimation of variance

The acoustic and swept area survey indices are presented together with an estimate of uncertainty (coefficient of variation; CV). These estimates are obtained from the bootstrap routine presented under the analysis section of Table 2. In the bootstrap of acoustic indices, each transect is treated as the primary sampling unit. In addition, a bootstrap routine for all trawl stations by strata is carried out within each run. The estimated CV (Standard Deviation ∙ 100/mean) is estimated from 500 iterations.

References

See section 10 in main report.

12 - Appendix 2. Changes in survey design, methods, gear etc.

Year Change from To
1984 Representative age sample, 100 per station Stratified age sample, 5 per 5-cm length group
1986 1 research vessel, 2 commercial trawlers 2 research vessels, 1 commercial trawler
1987 60 min. tow duration 30 min. tow duration
1989 Bobbins gear Rock-hopper gear (time series adjusted for cod and haddock)
1990 Random stratified bottom trawl stations Simrad EK400 echo sounder Fixed station grid, 20 nm distance Simrad EK500 echo sounder and BEI post processing
1993 TS = 21.8 log L – 74.9 for cod and haddock Fixed survey area (ABCD), 1 strata system, 35 strata Fixed station grid, 20 nm distance No constraint technique (strapping) on bottom trawl doors 5 age samples per 5-cm group, 2 per stratum Weighting of age-length keys by total catch TS = 20 log L – 68 for all demersal species (time series corrected) Extended, variable survey area (ABCDD’ES) 2 strata systems, 53 + 10 strata Fixed station grid, 20/30/40 nm distance Constraint technique on some bottom trawl hauls 2 age samples per 5-cm group, 4 per stratum (cod and haddock) Weighting of ALK by swept area estimate
1994 35-40 mm mesh size in cod-end Strapping on some hauls 22 mm mesh size in cod-end Strapping on every 3. haul
1995 Hull mounted transducers Variable use of trawl sensors Constant effective fishing width of the trawl Strapping on every 3. haul 2 research vessels, 1 commercial trawler Keel mounted transducers Johan Hjort Trawl manual specifying use of sensors Fish size dependent effective fishing width (time series corrected) Strapping on every 2. haul 3 research vessels
1996 2 strata systems and 63 strata, 20/30/40 nm distance 2 age samples per 5-cm group, 4 per stratum 1 strata system and 23 strata, 16/24/32 nm distance 1 age sample per 5-cm group, all stations with > 10 specimens (cod and haddock)
1997 1998 2000 16/24/32 nm distance Hull mounted transducers Strapping on every 2. haul 20 nm distance 3 Norwegian research vessels 20 nm distance Keel mounted transducers G.O. Sars Strapping on every haul 20/30 nm distance 2 Norwegian and 1 Russian research vessel
2002 20/30 nm distance station grid 16/20/24/32 nm distance station grid
2003 2004 2005 2006 2007 2008 2010 2011 2014 2015 Height trawl sensor for opening and bottom contact Vaco trawl doors EK 500 Sarsen EK 500 Standard Campelen rigging BEI V trawl doors V trawl doors 30 min. tow duration 1 strata system and 23 strata “Tromsø rigging” on Norwegian vessels Trawl eye for opening and bottom contact V- doors G.O. Sars and Johan Hjort ER60 G.O. Sars ER60 Johan Hjort and Russian vesselsTromsø rigging” on Norwegian vessels LSSS Norwegian vessels Thyborøn doors Jan Mayen/Helmer Hanssen Thyborøn doors G.O. Sars and Johan Hjort 15 min. tow duration 1 strata system and 26 strata (extended area N) Standard Campelen rigging
2017 Swept area estimates by the Survey Program Swept area and CV estimates by StoX software
  EK 60 on G.O. Sars EK80 in EK 60 modus on G.O. Sars
2018 Acoustic estimates by the BEAM Program Acoustic and CV estimates by StoX software
2020 2021 EK 60 on Johan Hjort Area N not included in standard time series Area N not included in standard time series EK80 in EK 60 modus on Johan Hjort Area N included in haddock survey indices Area N included in cod survey indices

13 - Appendix 3. Scientific participants 2022

Research vessel Participants
Helmer Hanssen” (18.01-16.02) Part 1 (18.01-01.02) T. Wenneck (cruise leader) , H. Haraldsen, S. Gundersen, H. Savolainen, E. Langhelle, J. F. Wilhelmsen, J. Kristiansen Part 2 (01.02-16.02) A. Staby (cruise leader) , T. Wenneck, E. Langhelle, F. Midtøy, C.E. Bjånes, J. F. Wilhelmsen
Johan Hjort” (27.01-14.03) Part 1 (27.01-03.02) J. A. Godiksen (cruise leader) , H. Mjanger, A. Berge, E. Odland, A.M. Aase, J. Nesheim, L.J. Ohnstad Part 2 (03.02-25.02) E. Fuglebakk (cruise leader) , A. Berge, G. Thorsheim, E. Holm, I. Huse, J. Nesheim, L.J. Ohnstad Part 3 (25.02-02.03, Vardø-Nord plankton transect) M. Martinussen (cruise leader) , H. Arnesen, M. Mjanger, H. Rognaldsen, J. Skjefstad Part 4 (02.03-14.03) K. Korsbrekke (cruise leader) , H. Mjanger, B. Stock, C.E. Bjånes, G. Thorsheim, E. Odland, S.E. Seim, E. Hermanssen, M. Mjanger, H. Rognaldsen, J. Skjefstad
Vilnyus” (21.01-26.02) A. Amelkin (cruise leader) , M. Osipov, M. Gubanischev, А . К anischev, S. Kharlin, M. Nosov, Yu. Kalashnikov, M. Rybakov, A. Benzik D. Draganov, T. Mishin, A. Bessonov, M. Kalashnikova

14 - Appendix 4. Annual survey reports 1981-2021

Dalen, J., Hylen, A. og Smedstad, O. M. 1981. Intern toktrapport unummerert. Havforskningsinstituttet.

Dalen, J., Hylen, A., Jakobsen, T., Nakken, O., Randa, K. and Smedstad, O. 1982. Norwegian investigations on young cod and haddock in the Barents Sea during the winter 1982. ICES CM 1982/G: 41, 20 pp.

Dalen, J., Hylen, A., Jakobsen, T., Nakken, O., Randa, K., and Smedstad, O. 1983. Preliminary report of the Norwegian investigations on young cod and haddock in the Barents Sea during the winter 1983. ICES CM 1983/G:15, 23 pp

Dalen, J., Hylen, A., Jakobsen, T., Nakken, O. and Randa, K. 1984. Preliminary report of the Norwegian Investigations on young cod and haddock in the Barents Sea during the winter 1984. ICES CM 1984/G:44, 26 pp.

Hylen, A., Jakobsen, T., Nakken, O. and Sunnanå, K. 1985. Preliminary report of the Norwegian Investigations on young cod and haddock in the Barents Sea during the winter 1985. ICES CM 1985/G:68, 28 pp.

Hylen, A., Jakobsen, T., Nakken, O., Nedreaas, K. and Sunnanå, K. 1986. Preliminary report of the Norwegian Investigations on young cod and haddock in the Barents Sea. ICES CM 1986/G:76, 25 pp.

Godø, O. R., Hylen, A., Jacobsen, J. A., Jakobsen, T., Mehl, S., Nedreaas, K. and Sunnanå, K. 1987. Estimates of stock size of Northeast Arctic cod and haddock from survey data 1986/1987. ICES CM 1987/G: 37.

Hylen, A., Jacobsen, J.A., Jakobsen, T., Mehl, S., Nedreaas, K. and Sunnanå, K. 1988. Estimates of stock size of Northeast Arctic cod and haddock, Sebastes mentella and Sebastes marinus from survey data, winter 1988. ICES CM 1988/G: 43.

Jakobsen, T., Mehl, S., Nakken, O., Nedreaas, K. and Sunnanå, S. 1989. Estimates of stock size of Northeast Arctic cod and haddock, Sebastes mentella and Sebastes marinus from survey data, winter 1989. ICES CM 1989/G: 42.

Jakobsen, T., Mehl, S. og Nedreaas, K. 1990. Kartlegging av mengde og utbredelse av torsk, hyse og uer i Barentshavet januar mars 1990. Intern toktrapport, Senter for marine ressurser, Havforskningsinstituttet, Bergen. Engelsk abstrakt, tabell og figurtekster. 29 s. (upubl.).

Hylen, A., Jakobsen, T., Mehl, S., og Nedreaas, K. 1991. Undersøkelser av torsk, hyse og uer i Barentshavet vinteren 1991. Intern toktrapport nr. 1 -1992, Senter for marine ressurser, Havforskningsinstituttet, Bergen. Engelsk abstrakt, tabell og figurtekster. 30 s. (upubl.).

Godø, O.R., Jakobsen, T., Mehl, S., Nedreaas, K. og Raknes, A. 1992. Undersøkelser av torsk, hyse og uer i Barentshavet vinteren 1992. Intern toktrapport 39/92, Senter for marine ressurser, Havforskningsinstituttet, Bergen. Engelsk abstrakt, tabell og figurtekster. 33 s. (upubl.).

Korsbrekke, K., Mehl, S., Nakken, O. and Nedreaas, K. 1993. Bunnfiskundersøkelser i Barentshavet vinteren 1993. Rapp. Senter Marine Ressurser nr. 14-1993. Engelsk abstrakt, tabell- og figurtekster. 47s. Havforskningsinstituttet, Bergen.

Mehl, S. og Nakken, O. 1994. Bunnfiskundersøkelser i Barentshavet vinteren 1994. Fisken Hav (6) 1994. 72 s. Havforskningsinstituttet, Bergen.

Korsbrekke, K., Mehl, S., Nakken, O. og Sunnanå, K. 1995. Bunnfiskundersøkelser i Barentshavet vinteren 1995. Fisken Hav (13) 1995. 86 s. Havforskningsinstituttet, Bergen.

Mehl, S. og Nakken, O. 1996. Botnfiskundersøkingar i Barentshavet vinteren 1996. Fisken Hav (11) 1996. 68 s. Havforskingsinstituttet, Bergen.

Mehl, S. 1997. Botnfiskundersøkingar i Barentshavet (norsk sone) vinteren 1997. Fisken Hav (11) 1997. 72 s. Havforskingsinstituttet, Bergen.

Mehl, S. 1998. Botnfiskundersøkingar i Barentshavet (redusert område) vinteren 1998. Fisken Hav (7) 1998. 69 s. Havforskingsinstituttet, Bergen.

Mehl, S. 1999. Botnfiskundersøkingar i Barentshavet vinteren 1999. Fisken Hav (13) 1999. 70 s. Havforskingsinstituttet, Bergen.

Aglen, A., Drevetnyak, K., Jakobsen, T., Korsbrekke, K., Lepesevich, Y., Mehl, S., Nakken, O. and Nedreaas, K. 2001. Investigations on demersal fish in the Barents Sea winter 2000. Detailed report. IMR-PINRO Joint Report Series no. 5, 2001. 74 pp.

Aglen, A., Alvsvåg, J, Korsbrekke, K., Lepesevich, Y., Mehl, S., Nedreaas, K., Sokolov, K. and Ågotnes, P. 2002. Investigations on demersal fish in the Barents Sea winter 2001. Detailed report. IMR-PINRO Joint Report Series no. 2 2002, 66 pp.

Aglen, A., Alvsvåg, J., Drevetnyak, K, Høines, Å., Korsbrekke, K., Mehl, S., and Sokolov, K. 2002. Investigations on demersal fish in the Barents Sea winter 2002. Detailed report. IMR/PINRO Joint report series no 6, 2002. 63 pp.

Aglen, A., Alvsvåg, J., Halland, T.I., Høines, Å., Nakken, O., Russkikh, A., and., Smirnov, O. 2003. Investigations on demersal fish in the Barents Sea winter 2003. Detailed report. IMR/PINRO Joint report series no 1, 2003. 56pp.

Aglen, A., Alvsvåg, J., Høines, Å., Korsbrekke, K., Smirnov, O., and Zhukova, N., 2004. Investigations on demersal fish in the Barents Sea winter 2004. Detailed report. IMR/PINRO Joint report series no 5/2004, ISSN 1502-8828. 58pp.

Aglen, A., Alvsvåg, J., Grekov, A., Høines, Å., Mehl, S., and Zhukova, N. 2005. Investigations of demersal fish in the Barents Sea winter 2005. IMR/PINRO Joint Report Series, No 4/2005. ISSN 1502-8828, 58 pp.

Aglen, A., Alvsvåg, J., Høines, Å., Johannesen, E. and Mehl, S. 2008. Investigations on demersal fish in the Barents Sea winter 2006. Detailed report. Fisken Hav13 (2008). 49 pp.

Aglen, A. 2007. Report from demersal fish survey in the Barents Sea February-March 2007. WD #8 ICES Arctic Fisheries Working Group, Vigo, Spain 19-28 April 2007.

Aglen, A., Høines, Å., Mehl, S., Prozorkevich, D., Smirnov, O. and Wenneck, T. de L. 2008. Results from the Joint IMR-PINRO Barents Sea demersal fish survey 25 January – 14 March 2008. WD #16 ICES Arctic Fisheries Working Group, ICES Headquarters 21-29 April 2008.

Aglen, A., Alexandrov, D., Høines, Å., Mehl, S., Prozorkevich, D. and Wenneck, T. de L. 2009. Results from the Joint IMR-PINRO Barents Sea demersal fish survey 1 February – 15 March 2009. WD #11 ICES Arctic Fisheries Working Group, San-Sebastian, Spain 21-27 April 2007.

Aglen, A., Alexandrov, D., Gjøsæter, H., Johannesen, E., Mehl, S. and Wenneck, T. de L. 2010. Results from the Joint IMR-PINRO Barents Sea demersal fish survey 1 February – 17 March 2010. WD #15 ICES Arctic Fisheries Working Group, Lisbon, Portugal/Bergen, Norway 22-28 April 2010.

Aglen, A., Alexandrov, D., Gjøsæter, H., Johannesen, E. and Mehl, S. 2011. Results from the Joint IMR-PINRO Barents Sea demersal fish survey 1 February – 14 March 2011. WD #3 ICES Arctic Fisheries Working Group, Hamburg, Germany 28 April - 4 May 2011.

Aglen, A., Dingsør, G., Mehl, S., Murashko, P. and Wenneck, T. de L. 2012. Results from the Joint IMR-PINRO Barents Sea demersal fish survey 21 January – 15 March 2012. WD #3 ICES Arctic Fisheries Working Group, Copenhagen, Denmark 20-26 April 2012.

Mehl, S., Aglen, A., Alexandrov, D.I., Bogstad, B., Dingsør, G.E., Gjøsæter, H., Johannesen, E., Korsbrekke, K., Murashko, P.A., Prozorkevich, D.V., Smirnov, O.V., Staby, A., and Wenneck, T. de Lange, 2013. Fish investigations in the Barents Sea winter 2007-2012. IMR/PINRO Joint Report Series 1-2013, 97 pp.

Aglen, A., Dingsør, G., Godiksen, J., Gjøsæter, H., Johannesen, E. and Murashko, P. 2013. Results from the Joint IMR-PINRO Barents Sea demersal fish survey 1 February – 13 March 2013. WD #3 ICES Arctic Fisheries Working Group, Copenhagen, Denmark 18-24 April 2013.

Aglen, A., Godiksen, J., Gjøsæter, H., Mehl, S., Russkikh, A. and Wenneck, T. de L. 2014. Results from the Joint IMR-PINRO Barents Sea demersal fish survey 22 January – 8 March 2014. WD #3 ICES Arctic Fisheries Working Group, Lisbon, Portugal 23-29 April 2014.

Mehl, S., Aglen, A., Bogstad, B., Dingsør, G.E., Gjøsæter, H., Godiksen, J., Johannesen, E., Korsbrekke, K., Murashko, P.A., Russkikh, A.A, Staby, A., Wenneck, T. de Lange, Wienerroither, R. 2014. Fish investigations in the Barents Sea winter 2013-2014. IMR/PINRO Joint Report Series 2014(2), 73 pp. ISSN 1502-8828.

Mehl, S. Aglen, A., Amelkin, A., Dingsør, G.E., Gjøsæter, H., Godiksen, Staby, A., Wenneck, T. de Lange, Wienerroither. 2015. Fish investigations in the Barents Sea, winter 2015. IMR-PINRO report series 2-2015. 61 pp.

Mehl, S., Aglen, A., Amelkin, A.V., Bogstad, B., Dingsør, G., Korsbrekke, K., Olsen, E., Russkikh, A.A., Staby, A., Wenneck, T. de Lange and Wienerroither, R. 2016. Fish investigations in the Barents Sea winter 2016. IMR/PINRO Joint Report Series 2016-4, 76pp.

Mehl, S., Aglen, A., Bogstad, B., Russkikh, A.A., Staby, A., Wenneck, T. de Lange and Wienerroither, R. 2017. Fish investigations in the Barents Sea winter 2017. IMR/PINRO Joint Report Series 2017-3, 87pp.

Mehl, S., Aglen, A., Gjøsæter, H., Godiksen, J. A., Russkikh, A.A., Staby, A., Tretyakov, I., Wenneck, T. de Lange and Wienerroither, R. 2018. Fish investigations in the Barents Sea winter 2018. IMR/PINRO Joint Report Series 2018-1, 82pp.

Mehl, S., Wenneck, T. de Lange, Aglen, A., Fuglebakk, E., Gjøsæter, H., Godiksen, J. A., Seim, S., Staby, A., Bogstad, B., Russkikh, A. and Fomin, K. 2019. Fish investigations in the Barents Sea winter 2019. IMR/PINRO Joint Report Series: 4-2019, 84pp.

Fall, J., de Lange Wenneck, T., Bogstad, B., Fuglebakk, E., Gjøsæter, H., Seim, S. E., Skage, M. L., Staby, A., Tranang, C. A., Windsland, K., Russkikh, A. A., Fomin, K. 2020. Fish investigations in the Barents Sea winter 2020. IMR/PINRO Joint Report Series: 2-2020, 98 pp.

Fall, J., de Lange Wenneck, T., Bogstad, B., Fuglebakk, E., Godiksen, J.A., Korsbrekke, K., Seim, S. E., Skage, M. L., Staby, A., Tranang, C. A., Windsland, K., Russkikh, A. A., Kharlin, S. 2021. Fish investigations in the Barents Sea winter 2021. IMR/PINRO Joint Report Series: 1-2022, 100 pp.

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